Ore analysis method

Abstract

Provided is an ore analysis method comprising: a consolidated piece preparation step for preparing a consolidated piece in which a powdery ore sample and a resin are mixed; a sliced sample preparation step for preparing, from the consolidated piece, a sliced sample having a thickness equal to or less than a depth at which it is possible to acquire a transmission image having added thereto elemental information of the ore sample by using an X-ray analysis microscope; and an X-ray analysis microscope analysis step for detecting particles containing a metal of interest contained in the sliced sample by using the X-ray analysis microscope, and ascertaining the positions of the particles containing the metal of interest in the sliced sample.

Description

Methods for analyzing ore

[0001] The present invention relates to a method for analyzing ore.

[0002] When recovering one or more metals (sometimes referred to as "target metals" in this invention) selected from high-value metals such as gold and platinum group metals from ore, the optimal method and conditions are selected according to the mineral form, content ratio, location (distribution), shape, particle size, particle size distribution, bonding state, etc., of the particles containing the target metals (sometimes referred to as "target metal particles" in this invention) in the target ore. Therefore, it is necessary to understand this information in advance.

[0003] For example, gold often exists as native gold particles in gold ore, but it can also exist as gold mineral particles such as silver-containing electrum or gold telluride. Furthermore, gold particles can coexist with quartz, as well as with sulfide minerals such as copper sulfide, arsenopyrite, and pyrite. Gold is also a metal with an extremely low abundance in the Earth's crust.

[0004] To obtain the above information, there is a method that uses an automated mineral identification analyzer (MLA) to analyze (1) the mineral form and content ratio (mineral ratio), (2) the particle size and particle size distribution for each mineral, and (3) the bonding state in ores containing metallic elements such as copper, nickel, gold, and platinum. For example, Patent Document 1 discloses a method for surface analysis of mineral particles using an MLA.

[0005] In analysis using MLA, the amount to be measured (the number of polished pieces to be measured) is determined by considering the elemental concentration of the metal of interest in the ore. For example, in the analysis of ore with a trace amount of gold (on the order of ppm), such as gold ore, about 10 or more polished pieces are prepared and the analysis is performed using MLA.

[0006] Japanese Patent Publication No. 2018-81092

[0007] However, even when 10 or more polished pieces are prepared from an ore sample and analyzed by MLA, the number of target metal particles detected may be small. To illustrate with a specific example, in the case of gold ore, MLA analysis makes it difficult to determine whether or not coarse-grained gold (coarse gold particles with a particle size of about 50 μm) is present in the polished piece if it is not exposed on the surface. In addition, there were two problems: the number of gold particles that could be analyzed was small to begin with, and it was unclear whether the mineral morphology and bonding state (single element, single-edged, inclusion) of the detected and measured gold particles guaranteed representativeness in the gold ore.

[0008] One possible solution to these problems is to increase the number of polished pieces and perform MLA analysis. However, in the case of gold ore, for example, depending on the gold grade of the ore, it is thought that it would be necessary to prepare more than 10 times the current amount of polished pieces (more than 100 pieces) and perform MLA analysis. If the number of polished pieces is set at 100, the MLA analysis time per gold ore sample alone would be approximately 400 hours, and considering the man-hours required for polished piece preparation and the MLA analysis time, this presents a challenge as it is not a practical approach. Therefore, the present invention aims to provide an ore analysis method that can perform ore analysis more efficiently than conventional ore analysis methods.

[0009] To solve the above-mentioned problems, the inventors conducted research on improving the efficiency of ore analysis. They then conceived the idea that by analyzing ore using an X-ray analytical microscope and / or an X-ray CT scanner, it would be possible to perform ore analysis more efficiently than with conventional ore analysis methods, and thus completed the present invention.

[0010] That is, the first invention that solves the above-mentioned problems is a method for analyzing ore, comprising: a solidified piece preparation step of preparing a solidified piece by mixing a powdered ore sample with a resin; a sliced ​​sample preparation step of preparing a sliced ​​sample having a thickness of less than or equal to a depth at which a transmission image with elemental information of the ore sample can be obtained using an X-ray analytical microscope from the solidified piece; and an X-ray analytical microscope analysis step of detecting particles containing the metal of interest contained in the sliced ​​sample using the X-ray analytical microscope and determining the position of the particles containing the metal of interest in the sliced ​​sample. The second invention is the method for analyzing ore according to the first invention, comprising: measuring the gray level of a compound or element constituting a mineral containing the metal of interest using an X-ray CT apparatus, determining a gray level threshold for identifying the compound or element containing the metal of interest, and in the sliced ​​sample preparation step, measuring the position of particles containing portions of the solidified piece that show a gray level threshold or higher in advance using an X-ray CT apparatus, and preparing a sliced ​​sample containing particles containing portions that show a gray level threshold or higher. The third invention is a method for analyzing ore according to the first or second invention, characterized by comprising: a cutting piece cutting step of cutting a cutting piece containing particles of the metal of interest from the sliced ​​sample based on the positional information of the particles of interest containing the metal of interest in the sliced ​​sample; and an X-ray CT measurement step of the cutting piece, in which an X-ray CT apparatus is used to measure the gray level of the particles of interest containing the metal of interest contained in the cutting piece, and one or more of the three-dimensional position, three-dimensional shape, particle size, and bonding state of the particles of interest containing the metal of interest in the cutting piece are determined. The fourth invention is a method for analyzing ore according to the third invention, characterized in that, in the X-ray CT measurement step of the cutting piece, two or more cutting pieces are stacked and placed in an X-ray CT apparatus, the gray level of the particles of interest containing the metal of interest contained in the stacked cutting pieces is measured, and one or more of the three-dimensional position, three-dimensional shape, particle size, and bonding state of the particles of interest containing the metal of interest contained in each stacked cutting piece are determined.The fifth invention is a method for analyzing ore according to the third invention, characterized by comprising: a step of preparing a cross-section sample of particles containing the metal of interest from the cross-section based on one or more pieces of information such as the three-dimensional position, three-dimensional shape, particle size, and bonding state of the particles containing the metal of interest in the cross-section; and a step of analyzing the cross-section sample using a SEM-EDS device to analyze one or more pieces of information such as the shape of the particles containing the metal of interest and the mating minerals to which they are bonded by single-edged and / or inclusion. The sixth invention is a method for analyzing ore, comprising: a simulated sample preparation step of preparing a simulated sample in which a plurality of compounds or elements of different densities, including compounds or elements constituting a mineral containing a metal of interest, are arranged; a threshold determination step of measuring the gray level of the simulated sample using an X-ray CT apparatus and determining a threshold gray level for distinguishing compounds or elemental particles containing the metal of interest contained in the simulated sample; a solidified piece preparation step of preparing a solidified piece by mixing the powdered ore with a resin; and an X-ray CT measurement step of the solidified piece of which measures the gray level of the solidified piece using an X-ray CT apparatus and reconstructs a three-dimensional image obtained from the gray level by applying the threshold determined in the threshold determination step, thereby determining one or more of the three-dimensional position and three-dimensional shape of particles in the solidified piece that include a portion of the gray level above the threshold gray level. The seventh invention is a method for analyzing ore according to the sixth invention, characterized by comprising: a slice sample preparation step of preparing a slice sample from the solidified piece that contains a portion of particles including a portion that exceeds the gray level threshold and is observable as a whole using an X-ray analytical microscope; and an X-ray analytical microscope measurement step of measuring the slice sample with an X-ray analytical microscope to identify particles containing the metal of interest.The eighth invention is a method for analyzing ore according to the seventh invention, characterized by comprising: a cutting step of preparing a cutting piece containing particles of the metal of interest from the slice sample in which the presence of particles of the metal of interest has been determined by the X-ray analytical microscope measurement step; and an X-ray CT measurement step of the cutting piece in which the gray level of particles of the metal of interest contained in the cutting piece is measured using an X-ray CT device with a higher resolution than the X-ray CT measurement of the solidified piece, thereby determining one or more of the three-dimensional position, three-dimensional shape, particle size, and bonding state of the particles of the metal of interest in the cutting piece. The ninth invention is a method for analyzing ore according to the eighth invention, characterized in that, in the X-ray CT measurement step of the cutting piece, two or more cutting pieces are stacked and placed in an X-ray CT device, the gray level of particles of the metal of interest contained in the stacked cutting pieces is measured, and one or more of the three-dimensional position, three-dimensional shape, particle size, and bonding state of the particles of the metal of interest contained in each stacked cutting piece is determined. The tenth invention is a method for analyzing ore according to the eighth invention, characterized by comprising: a step of preparing a cross-section sample of particles containing the metal of interest from the cross-section based on one or more pieces of information such as the three-dimensional position, three-dimensional shape, particle size, and bonding state of the particles containing the metal of interest in the cross-section; and a step of analyzing the cross-section sample using a SEM-EDS device to analyze one or more pieces of information such as the shape of the particles containing the metal of interest, and the mating minerals to which they are bonded by single-edge and / or inclusion. The eleventh invention is a method for analyzing ore according to any one of the first, second, sixth, seventh, eighth, ninth, or tenth inventions, characterized in that the metal of interest is gold and one or more metals selected from the platinum group. The twelfth invention is a method for analyzing ore according to the eleventh invention, characterized in that the metal of interest is gold.

[0011] By performing the ore analysis method according to the present invention, it is possible to perform ore analysis more efficiently compared to conventional ore analysis methods.

[0012] This is a process flow diagram of the ore analysis method. This is a graph showing the correspondence between the density of each compound or element and the gray level measurement results of each compound or element contained in a simulated sample as one embodiment of the present invention. This is a schematic perspective view of a simulated sample as one embodiment of the present invention. This is a gray level histogram of the solidified piece in Example 1. This is an X-ray CT image of the solidified piece in Example 1. This is a full-surface mapping image of the sliced ​​sample in Example 1 using an X-ray analytical microscope. This is a high-resolution mapping image of the gold particle (#1) shown in Figure 6. This is a high-resolution mapping image of the gold particle (#2) shown in Figure 6.

[0013] The embodiments for carrying out the present invention will be described in the following order, with reference to the process flow chart of the ore analysis method according to the present invention shown in Figure 1: [1] Preparation of solidified pieces, [2] Preparation of sliced ​​samples and analysis by X-ray analytical microscope, [3] Application of X-ray CT device during sliced ​​sample preparation, [4] Preparation of cut pieces containing particles containing the metal of interest, [5] Measurement of cut pieces containing particles containing the metal of interest using an X-ray CT device, [6] Analysis of the cut surface sample of particles containing the metal of interest using an SEM-EDS device, and [7] Summary. In Figure 1, the areas enclosed by solid lines indicate analysis and measurement steps using each device, the areas enclosed by dashed or long dashed lines indicate analysis and measurement steps to be performed as desired, and the underlines indicate samples used in each analysis and measurement step.

[0014] [1] Preparation of solidified pieces A solidified piece is prepared by mixing a powdered ore sample with an appropriate resin. The ore sample is in the state of powder obtained by crushing ore. There are no particular restrictions on the resin used, but epoxy resin can be preferably used from the viewpoint that a large amount can be prepared at once. Phenolic resin can also be used. The mixing ratio of the ore sample to the resin is preferably about 5 mL of epoxy resin for about 10 g of ore sample. The size of the solidified piece should be a size that can be loaded into an X-ray CT apparatus and corresponds to the FOV (Field of View) of the X-ray CT apparatus (X-ray CT apparatus and FOV will be described later). For example, the diameter of the solidified piece is preferably φ25 mm and the height is preferably 15 to 20 mm.

[0015] [2] Preparation of sliced ​​samples and analysis using an X-ray analytical microscope The inventors have been researching ways to improve the efficiency of ore analysis and have come to the realization that by using an X-ray analytical microscope, it is possible to discover metal particles of interest, including gold particles, contained in the solidified piece according to the present invention, and to grasp the two-dimensional positional information of the discovered metal particles of interest within the solidified piece.

[0016] (1) About the X-ray analytical microscope In this invention, the X-ray analytical microscope is a device that analyzes a sample using the principle of fluorescence X-ray analysis. With the X-ray analytical microscope, by focusing X-rays and irradiating the sample, it is possible to analyze elements in minute parts up to a depth of several millimeters. In addition, by scanning the sample in the X and Y axes, mapping analysis (surface analysis) can be performed to investigate the distribution of elements in the sample. Furthermore, it is equipped with a detector for transmitted X-rays, which allows for investigation of the internal condition of the sample.

[0017] X-ray analytical microscopes have the following characteristics: (I) By irradiating a sample with X-rays and simultaneously detecting the transmitted X-rays and generated fluorescent X-rays (XRF), it is possible to obtain a transmission image of the sample with added elemental information. (II) Multiple samples can be analyzed at once. (III) While the electron beam penetration depth of MLA is a maximum of several micrometers, the X-rays of an X-ray analytical microscope are a maximum of several millimeters, allowing information to be obtained from a range of up to several millimeters from the surface of the sample.

[0018] (2) Regarding sliced ​​samples, the inventors conceived that by using the features of the X-ray analytical microscope described above, they could perform mapping analysis (surface analysis) on metal particles contained in a sample processed from a solidified piece using an X-ray analytical microscope, and obtain complex two-dimensional information by superimposing the X-ray transmission image and elemental information of the target metal particles, including gold particles, contained in the sample in the thickness direction. They also conceived that they could screen for the target metal particles in the sample and measure and understand the two-dimensional position of the target metal particles. Specifically, they conceived that they could prepare sliced ​​samples by processing the solidified piece prepared in "[1] Preparation of Solidified Piece" to a size that can be loaded into an X-ray analytical microscope and to a predetermined thickness, load these into an X-ray analytical microscope, and use the X-ray analytical microscope as a screening analyzer for the target metal particles contained in the sliced ​​sample.

[0019] X-ray analytical microscopy analysis allows for the detection of small-particle metal particles of interest that cannot be detected by X-ray CT scanners with low-resolution FOV. Furthermore, by setting the thickness of the sliced ​​sample to a depth below which a transmission image with elemental information can be obtained using X-ray analytical microscopy, it becomes possible to screen for the metal of interest contained in coarse, high-brightness particles, as well as small-particle metal particles of interest that could not be detected by X-ray CT scanners, regardless of their location within the sliced ​​sample. It was also conceivable that the position of these metal particles of interest relative to the top surface of the sliced ​​sample could be measured and determined. Moreover, it was conceivable that the morphology and particle size of the metal particles of interest, as viewed from the X-ray transmission direction of the X-ray analytical microscope, could also be measured.

[0020] In contrast, X-ray CT scanners have the advantage of being able to acquire information about the presence of three-dimensional metal particles over a wide area. However, the information obtained is merely an X-ray transmission image and not information about the presence of the metal element of interest. Therefore, in this respect as well, there is a high possibility of detection failure.

[0021] In the X-ray analytical microscope investigated by the present inventors, when the thickness of the sliced ​​sample is 2 mm or less, preferably 1 mm or less, it was possible to obtain a transmission image with elemental information of the target metal particles (e.g., gold particles) contained in the sliced ​​sample, from the viewpoint of sufficiently detecting transmitted X-rays and generated fluorescent X-rays.

[0022] In contrast, conventional MLA analysis uses electron beams, which only penetrate 0.1 μm to several μm into the sample. Therefore, it was difficult to detect target metal particles located several μm or more below the sample surface. Consequently, hundreds or more polished pieces were prepared, and only those pieces in which the target metal particles happened to be present on the sample surface were selected for analysis. In particular, in the case of gold ore, as mentioned above, the gold content is trace (on the order of ppm), so there is a high possibility of missing gold particles if information obtained only from the surface of the sample is not sufficient. Moreover, the inability to detect coarse gold grains of about φ50 μm has a significant impact, resulting in a large discrepancy with the content rate determined by chemical analysis. To avoid this, MLA analysis required the preparation and measurement of a vast number of polished pieces.

[0023] [3] Application of X-ray CT device during slice sample preparation (1) Purpose of applying an X-ray CT device during slice sample preparation As explained in "[2] Slice sample preparation and analysis by X-ray analytical microscope (2) About slice samples", when preparing a slice sample according to the present invention by processing a solidified piece to a predetermined size and thickness, it is possible to prepare the slice sample by processing the solidified piece, for example, by cutting it at an arbitrary position. However, if the solidified piece is measured using an X-ray CT device before processing and the position of high-brightness particles (high-brightness particles will be described later) present in the solidified piece is known in advance, the processing position of the solidified piece can be determined so as to include the high-brightness particles, and the loss of high-brightness particles due to the processing operation can be avoided, so it is a preferred configuration to implement.

[0024] Specifically, based on the positional information of high-brightness particles contained in the solidified fragment obtained by measurement using an X-ray CT scanner, slice samples containing coarse high-brightness particles and having the aforementioned size are prepared from the solidified fragment and analyzed using an X-ray analytical microscope. The target metal contained in the coarse high-brightness particles, as well as target metal particles with small particle sizes that could not be detected by the X-ray CT scanner, are screened, and their positions are measured from the top surface of the slice sample. Furthermore, the shape and particle size of the target metal particles are also measured from the direction of X-ray transmission using the X-ray analytical microscope.

[0025] (2) X-ray CT apparatus In the present invention, an X-ray CT apparatus is an apparatus that irradiates a sample with X-rays from multiple directions, measures the transmitted X-ray intensity distribution with a detector, and reconstructs the distribution of X-ray permeability inside the sample as a three-dimensional image by calculation from the obtained data.

[0026] According to the X-ray CT scanner, by utilizing the difference in "ease of penetration" and "ease of absorption" of X-rays as they pass through the sample, a transmission contrast image corresponding to the density difference of the components can be obtained. Furthermore, by rotating the sample 360° and taking X-ray images from multiple angles, and performing image reconstruction processing, it is possible to non-destructively evaluate the three-dimensional structure, including the interior of the sample. For example, low-density components (e.g., silicate minerals: 3 g / cm³) can be evaluated. ３ Sulfide minerals: 5 g / cm³ ３ (etc.) were observed at low brightness, and high-density components (e.g., native gold: 19 g / cm³) were observed. ３ Electrum (AuAg): 15 g / cm³ ３ These are observed at high brightness.

[0027] As described above, the metal particles of interest in gold ore, including gold particles, are metal particles with a higher density and linear absorption coefficient compared to the matrix components (silicate minerals), and are therefore observed as high-brightness particles with high gray level values ​​in X-ray CT measurements. For example, in gold ore, because the density difference and the difference in linear absorption coefficient between the matrix components (silicate minerals) and the metal particles of interest are large, a gray level threshold can be set in the X-ray CT apparatus for identifying the metal of interest, and particles having a gray level above this threshold can be identified as high-brightness particles. Through this identification, high-brightness particles contained in the solidified fragment (many of which are considered to be the metal particles of interest) can be identified and extracted, and as a result, the metal particles of interest can also be extracted, which is a desirable configuration (the method for determining the gray level threshold for identifying high-brightness particles containing the metal of interest from the matrix components will be described later). This configuration is extremely effective in finding high-brightness particles from samples that contain only small amounts of high-brightness particles, such as solidified fragments made from gold ore. The X-rays are CuKα rays, and their wavelength is 1.54 Å.

[0028] Furthermore, X-ray CT scanners have two characteristics: FOV (field of view) and resolution. FOV and resolution are determined by the positional relationship between the X-ray source and the sample. Increasing the FOV also increases the minimum pixel size (voxel size), which decreases the resolution. Conversely, reducing the voxel size to increase resolution necessitates reducing the FOV, creating a trade-off relationship.

[0029] When determining the cutting position of the solidified fragment, setting a low-resolution FOV that allows the entire solidified fragment to be in view makes it possible to measure and understand the positional information of coarse, high-brightness particles within the ore sample, as described above. Many of these coarse, high-brightness particles are coarse metal particles of interest. As a result, it becomes possible to identify the coarse metal particles of interest contained in the solidified fragment, and the various analytical results of these metal particles of interest can ensure the representativeness of those metal particles in the ore, which is desirable. For example, since the size of the solidified fragment is about φ25 mm × 20 mm, the FOV of the X-ray CT apparatus will be set to about 25, and the voxel size will be about 9 μm.

[0030] As a result, even for the target metal particles, those with a small particle size or those with a special shape such as flat plate-shaped target metal particles having a small projected area in the X-ray irradiation direction may have a reduced apparent gray level and become less than the threshold value, and may not be detected as high-intensity particles.

[0031] As will be described later in the examples, according to the study by the present inventors, by setting the FOV of the X-ray CT apparatus to 25 and setting the threshold value of the gray level to 1500, high-intensity particles having a sphere equivalent diameter of about 3 μm could be detected. On the other hand, since the particle diameter of the coarse target metal particles to be grasped at the time of preparing the slice sample according to the present invention is about 50 μm, it is considered that there is no particular problem even with the resolution of FOV 25.

[0032] However, when it is desired to grasp the position of smaller target metal particles less than 50 μm in the consolidated piece, by miniaturizing the consolidated piece, the FOV at the time of measurement by the X-ray CT apparatus can be reduced below 25, the voxel size can be reduced, and the resolution can be increased.

[0033] (3) Measurement method using an X-ray CT apparatus Regarding the determination of the threshold value of the gray level used when measuring an ore sample with an X-ray CT apparatus and detecting high-intensity particles, it will be described by taking a gold ore sample as an example.

[0034] (I) Details of the preparation of the simulation sample will be described later in Example 1. A simulation sample in which a plurality of compounds or simple substances having different densities, including compounds or simple substances constituting a mineral containing a target metal and including each component of SiO, CuFeS, FeS, Fe, O, SUS, Cu, Pb coarse particles (φ270 μm), Au coarse particles (φ270 μm), and Au particles (φ70 μm), are arranged in the vertical direction was prepared. The density of each compound or simple substance in the simulation sample will be described in Example 1. ２ 、CuFeS ２ 、FeS ２ 、Fe ３ O ４ 、SUS, Cu, Pb coarse particles (φ2 μm), Au coarse particles (φ2 μm), and Au particles (φ70 μm), and a compound or simple substance containing a target metal, are arranged in the vertical direction. The density of each compound or simple substance in the simulation sample will be described in Example 1.

[0035] (II) Measurement of Gray Level and Determination of Threshold A simulated sample was loaded into an X-ray CT scanner, and the gray level of each component was measured. An example of the measurement results is shown in Figure 2. An example of the gray level measurement conditions will be explained in Example 1. In Figure 2, the horizontal axis is plotted the gray level of each component measured by the X-ray CT scanner, and the vertical axis is plotted the density value of each component, with solid lines connecting the plot points of each sample. From Figure 2, SiO ２ It was found that the gray level of Cu is below -500, while the gray levels of Pb and Au are above 3000.

[0036] SiO ２ The difference in gray levels between Cu (below -500) and Pb and Au (above 3000) is thought to be due to differences in density as well as different linear absorption coefficients. Metals with linear absorption coefficients close to the target metals Au, Os, Ir, and Pt are few in number, including Pb, Hg, Tl, Bi, Te, Po, U, etc., and therefore do not pose a particular problem in the implementation of the present invention. The target metals in the present invention are Au and platinum group metals. Au is particularly preferred. Among the platinum group metals, Os, Ir, and Pt are preferred.

[0037] Based on these test results, the inventors conceived of a configuration in which a gray level threshold for distinguishing particles containing the target metal from other components is determined from results obtained using a simulated sample. Specifically, for example, the gray level threshold is set to 1500, and particles with a gray level of 1500 or higher are distinguished as high-luminosity particles, and particles with a gray level below 1500 are distinguished as low-luminosity components (particles). Then, it was conceived that particles containing the target metal, and particles that are not the target metal but have a gray level equal to or higher than the target metal, can be separated and distinguished as high-luminosity particles, while other components (particles) can be distinguished as low-luminosity components (particles). For example, particles containing a metal such as Pb that is not the target metal but shows a gray level of 1500 or higher are judged to be high-luminosity particles. However, as mentioned above, there are few such metal species. Furthermore, such metal species can be easily excluded at the stage of analysis using an X-ray analytical microscope, which will be described later.

[0038] Then, by performing image reconstruction (imaging) on ​​the obtained histogram with a gray level of 1500 or higher, it is possible to determine at least one of the following: the three-dimensional position or the three-dimensional shape of high-luminance particles within the solidified piece.

[0039] [4] Preparation of a cut piece containing particles of the target metal Based on the results of the X-ray analytical microscope analysis described in "[2] Preparation of sliced ​​sample and analysis by X-ray analytical microscope" above, if the position of the target metal particles contained in the sliced ​​sample as viewed from the top surface of the sliced ​​sample can be measured and determined, then based on that positional information, the sliced ​​sample can be cut in the thickness direction so as to contain the target metal particles, and a cut piece containing particles of the target metal (sometimes referred to as a "cut piece" in this invention) can be prepared. As a result, the coarse target metal particles will be located somewhere in the thickness direction of the cut piece.

[0040] [5] Measurement of a section containing particles of the target metal using an X-ray CT scanner The inventors have come up with the idea that by measuring the above-mentioned section using the above-mentioned X-ray CT scanner and performing image reconstruction processing, it is possible to measure the position, shape, particle size, and other three-dimensional information of coarse target metal particles and other particles within the section, as well as the bonding state.

[0041] This is because, since the size of the section is, for example, about φ5 mm × height 1 mm, the FOV of the X-ray CT scanner can be set to about 5 to 7, and the voxel size is set to 2.1 to 2.5 μm, allowing for high-resolution analysis of high-brightness particles (at this stage, the target metal particles after screening by X-ray analytical microscopy).

[0042] Furthermore, since the thickness of the cut pieces is only about 1 to several millimeters, multiple cut pieces can be stacked in the thickness direction and loaded into the X-ray CT scanner, allowing for high-resolution measurement of the target metal particles. As a result, a single measurement using the X-ray CT scanner and image reconstruction process can simultaneously measure the three-dimensional position, three-dimensional shape, particle size, and bonding state of the target metal particles contained in multiple cut pieces, which is a desirable configuration from the standpoint of improving work efficiency.

[0043] [6] Analysis of cross-section samples of particles containing the metal of interest using an SEM-EDS instrument. As described above, high-resolution analysis using an X-ray CT instrument allows for the analysis of three-dimensional information of the metal of interest particles within the cross-section, as well as their bonding state (single, single-edged, inclusion). If it is desired to analyze the particle shape of the metal of interest particles more accurately, or information about the other minerals bonded to the metal of interest particles, it is also preferable to perform analysis using an SEM-EDS instrument.

[0044] However, similar to MLA, the penetration depth of the electron beam of the SEM-EDS device into the cut piece is only a few micrometers. However, since the position and three-dimensional information of the metal particles of interest within the cut piece are revealed by the analysis using an X-ray CT device as described in "[5] Analysis of a cut piece containing particles of interest using an X-ray CT device", it is easy to process the cut piece based on this position and three-dimensional information, and to expose the cross-section of the desired measurement location on the metal particles of interest, thereby creating a cut surface sample of the particles containing the metal of interest (sometimes referred to as a "cut surface sample" in this invention). Then, by performing carbon deposition or the like on the exposed cross-section of the cut surface sample and performing SEM-EDS measurement, the particle shape of the metal particles of interest and the bonding state of the mating mineral to which the metal particles of interest are bonded (single, single-edged, inclusion) can be analyzed in detail.

[0045] [7] Summary When the present invention is implemented, it is possible to analyze the bonding state and other aspects of the ore containing the metal particles of interest while ensuring representativeness, and to easily identify coarse metal particles of interest. Furthermore, the time required for operations from the solidification piece preparation process to the SEM-EDS analysis process was approximately 40 hours. This is less than one-tenth of the time required for operations using MLA with conventional technology, which required approximately 400 hours.

[0046] [Example 1] The present invention will be specifically explained using an example of an analysis method for metal particles of interest in a solidified piece containing gold ore, using a combination of an X-ray analytical microscope and an X-ray CT scanner. However, the present invention is not limited to this example.

[0047] (1) Setting a gray level threshold for detecting target metal particles from solidified fragments using an X-ray CT scanner. In order to detect target metal particles from solidified fragments and to set a gray level threshold for an X-ray CT scanner, a simulated sample was first prepared in which multiple compounds or elements of different densities, including a compound or element constituting the mineral containing the target metal, were arranged vertically. Using this simulated sample, a threshold was set that would allow for the separation and identification of the target metal from other components.

[0048] Figure 3 is a schematic perspective view of the simulated sample according to Example 1. The simulated sample according to Example 1 is SiO ２ (powder), CuFeS ２ (powder), FeS ２ (powder), Fe ３ O ４ It contains (powder), SUS (pieces), Cu (particles), Pb (φ270μm particles), Au (φ270μm particles), and Au (φ70μm particles).

[0049] Specifically, SiO ２ (powder), CuFeS ２ (powder), FeS ２ (powder), Fe ３ O ４ (powder), SUS (pieces), Cu (particles), Pb (φ270 μm particles), Au (φ270 μm particles), and Au (φ70 μm particles) were prepared as components of the simulated sample. SiO ２ CuFeS ２ FeS ２ Fe ３ O ４ Pellets with a diameter of 7 mm and a thickness of 1 mm were prepared by curing SUS and Cu with thermosetting epoxy resin, and Pb and Au particles with thermosetting epoxy resin. These pellets were stacked to prepare a simulated sample according to Example 1. The densities of each compound or element in the simulated sample according to Example 1 are shown in Table 1.

[0050]

[0051] The simulated samples according to Example 1 were loaded into an X-ray CT scanner (CT Lab HX130, manufactured by Rigaku Corporation), and the gray level of each sample was measured under the measurement conditions shown in Table 2. The measurement results are shown in Figure 2.

[0052] Figure 2 shows the gray level of each sample measured by an X-ray CT scanner on the horizontal axis and the density value of each sample on the vertical axis, with the plotted points of each sample connected by solid lines. From Figure 2, SiO ２ It was found that the gray level of Cu is below -500, while the gray levels of Pb and Au are above 3000.

[0053] SiO ２ The difference in gray levels between Cu (below -500) and Pb and Au (above 3000) is thought to be due to differences in density as well as different linear absorption coefficients. Metals with linear absorption coefficients close to those of the target metal, such as Au, Os, Ir, and Pt, are few in number, including Pb, Hg, Tl, Bi, Te, Po, and U, and therefore do not pose a particular problem in the implementation of this invention. The target metals in this invention are gold and platinum group metals. Gold is particularly preferred. Among the platinum group metals, Os, Ir, and Pt are preferred.

[0054] Based on these test results, the inventors conceived of a configuration in which a gray level threshold is set to distinguish between particles containing the target metal and other components in a simulated sample. Specifically, for example, the gray level threshold is set to 1500, and particles with a gray level of 1500 or higher are distinguished as high-luminance particles, and particles with a gray level below 1500 are distinguished as low-luminance components (particles). This makes it possible to separate and distinguish particles containing the target metal as high-luminance particles and other components (particles) as low-luminance components (particles). For example, metals such as Pb, which are not the target metal but exhibit a luminance of a gray level of 1500 or higher, are judged to be high-luminance particles. However, there are few such metal species. Furthermore, such metal species can be excluded at the stage of analysis using an X-ray analytical microscope, which will be described later, so this does not pose a particular problem. By performing image reconstruction processing (imaging) on ​​the obtained histogram of gray levels of 1500 or higher, it was possible to determine at least one of the following: the three-dimensional position or the three-dimensional shape of the high-luminance particles in the solidified piece.

[0055]

[0056] (2) Application of X-ray CT apparatus to solidified piece containing gold ore Gold ore a (gold grade 9 g / t) was prepared. Gold ore a was crushed to obtain gold ore sample A. Then, 10 g of the crushed gold ore sample A and about 5 g of epoxy resin were mixed to prepare a solidified piece (φ25 mm, height 20 mm) according to Example 1. The solidified piece according to Example 1 was loaded into an X-ray CT apparatus and the gray level was measured under the measurement conditions shown in Table 2. The obtained gray level histogram is shown in Figure 4.

[0057] Then, by setting the threshold to 1500 in the gray level histogram and processing the image reconstruction (imaging) of particles showing a value above this as high-luminance particles, high-luminance particles (equivalent spherical diameter: approximately 30 μm) were extracted, and three-dimensional information such as the position, shape, and particle size of these high-luminance particles in the solidified piece was obtained. Figure 5 is a cross-sectional view of the solidified piece according to Example 1, and shows the X-ray CT image of the position where the high-luminance particle was detected. In Figure 5, one high-luminance particle (#1) is detected in the peripheral area at the bottom of the cross-section. The enclosed area in the center of Figure 5 is an enlarged view of the high-luminance particle (#1).

[0058] (3) Preparation of sliced ​​samples Based on the position of the high-brightness particles in the solidified piece obtained in (2) above, the solidified piece was cut radially to prepare sliced ​​samples with a diameter of 25 mm and a thickness of 1 mm. At this time, the cutting position was determined based on the information from the X-ray CT image so that the high-brightness particles would be contained in the sliced ​​sample.

[0059] (4) Analysis of sliced ​​samples using an X-ray analytical microscope The prepared sliced ​​samples were loaded into an X-ray analytical microscope (Horiba, Ltd. XGT-9000) and mapping analysis was performed under the measurement conditions shown in Table 3.

[0060]

[0061] First, a mapping analysis was performed on the entire surface of the sliced ​​sample with a beam size of 100 μm. Figure 6 shows the mapping image of the entire surface. In Figure 6, gold particles (#1) were detected on the upper right side of the sliced ​​sample, and gold particles (#2) were detected on the lower side. The box in the upper right of Figure 6 is a magnified view of gold particle (#1), and the box in the lower left is a magnified view of gold particle (#2).

[0062] Full-surface mapping analysis of the sliced ​​sample detected two gold particles (#1 and #2). Of these two gold particles, one (#1) matched the high-brightness particle extracted by the X-ray CT scanner mentioned above. The other particle (#2) was not extracted as a high-brightness particle by the X-ray CT scanner. This indicates that X-ray analytical microscopy (beam size 100 μm) has a higher detection capability for gold particles than X-ray CT scanner (FOV 25).

[0063] Furthermore, analysis results for two gold particles (#1, #2) and other matrix portions were obtained from full-surface mapping analysis of the sliced ​​samples using an X-ray analytical microscope, which are shown in Table 4.

[0064]

[0065] The results in Table 4 show that silver was detected along with gold in two gold particles (#1 and #2), suggesting that these gold particles may be electrum.

[0066] On the other hand, in the mapping image with a beam size of 100 μm shown in Figure 6, the resolution of the images showing gold particles (#1, #2) was low, making it difficult to determine whether the gold particles were coarse-grained or not. Therefore, the beam size of the X-ray analytical microscope was set to 15 μm, and the area was narrowed to 1 mm square to perform high-resolution mapping analysis of the gold particles (#1, #2). The results are shown in Figure 7 for gold particle (#1) and Figure 8 for gold particle (#2). By reducing the beam size, high-resolution images of the gold particles were obtained. Furthermore, it was confirmed that gold particle (#1) was a coarse-grained gold particle with a particle size of approximately 50 μm, and gold particle (#2) was a coarse-grained gold particle with a particle size of approximately 80 μm, and their shapes were also confirmed.

[0067] The operation in Example 1 took approximately 40 hours. This is less than one-tenth the time required for the operation using conventional MLA technology, which took about 400 hours. Furthermore, it was possible to identify the representative bonding state of the gold ore and the coarse gold particles contained in the gold ore that could be analyzed.

Claims

1. A method for analyzing ore, comprising: a solidified piece preparation step of preparing a solidified piece by mixing a powdered ore sample with a resin; a sliced ​​sample preparation step of preparing a sliced ​​sample having a thickness less than or equal to the depth at which a transmission image with elemental information of the ore sample can be obtained using an X-ray analytical microscope from the solidified piece; and an X-ray analytical microscope analysis step of detecting particles containing the metal of interest contained in the sliced ​​sample using the X-ray analytical microscope and determining the position of the particles containing the metal of interest in the sliced ​​sample.

2. The method for analyzing ore according to claim 1, characterized in that an X-ray CT apparatus is used to measure the gray level of a compound or element constituting the mineral containing the metal of interest, a threshold for the gray level for identifying the compound or element containing the metal of interest is determined, and in the slice sample preparation step, the position of particles containing portions of the solidified piece that show a gray level threshold or higher is measured in advance using an X-ray CT apparatus, and a slice sample containing particles containing portions that show a gray level threshold or higher is prepared.

3. The ore analysis method according to claim 1 or 2, comprising: a cutting piece cutting step of cutting a cutting piece containing the particles of interest from the sliced ​​sample based on the positional information of the particles of interest containing the metal of interest in the sliced ​​sample; and an X-ray CT measurement step of the cutting piece, in which an X-ray CT apparatus is used to measure the gray level of the particles of interest containing the metal of interest contained in the cutting piece, and one or more of the three-dimensional position, three-dimensional shape, particle size, and bonding state of the particles of interest containing the metal of interest in the cutting piece is determined.

4. The method for analyzing ore according to claim 3, characterized in that, in the X-ray CT measurement step of the cut piece, two or more cut pieces are stacked and placed in an X-ray CT apparatus, the gray level of particles containing the metal of interest contained in the stacked cut pieces is measured, and one or more of the three-dimensional position, three-dimensional shape, particle size, and bonding state of particles containing the metal of interest contained in each stacked cut piece is determined.

5. The ore analysis method according to claim 3, comprising: a step of preparing a cross-section sample of particles containing the metal of interest from the cross-section based on one or more pieces of information on the three-dimensional position, three-dimensional shape, particle size, and bonding state of the particles containing the metal of interest in the cross-section; and a step of analyzing the cross-section sample using a SEM-EDS device to analyze one or more pieces of information on the shape of the particles containing the metal of interest, and the mating minerals to which they are bonded by single-edged and / or inclusion.

6. A method for analyzing ore, comprising: a simulated sample preparation step of preparing a simulated sample in which a plurality of compounds or elements of different densities, including a compound or element constituting a mineral containing a metal of interest, are arranged; a threshold determination step of measuring the gray level of the simulated sample using an X-ray CT apparatus and determining a threshold gray level for distinguishing compounds or element particles containing the metal of interest contained in the simulated sample; a solidified piece preparation step of preparing a solidified piece by mixing the powdered ore with a resin; and an X-ray CT measurement step of the solidified piece of which measures the gray level of the solidified piece using an X-ray CT apparatus and reconstructs a three-dimensional image obtained from the gray level by applying the threshold determined in the threshold determination step, thereby determining one or more of the three-dimensional position and three-dimensional shape of particles in the solidified piece that show a gray level above the threshold.

7. The method for analyzing ore according to claim 6, comprising: a slice sample preparation step of preparing a slice sample from the solidified piece that contains a portion of particles including a portion that exceeds the gray level threshold and that can be observed as a whole using an X-ray analytical microscope; and an X-ray analytical microscope measurement step of measuring the slice sample with an X-ray analytical microscope to identify particles containing the metal of interest.

8. The ore analysis method according to claim 7, comprising: a cutting step of preparing a cutting piece containing particles of the metal of interest from the slice sample in which the presence of particles of the metal of interest has been determined by the X-ray analytical microscope measurement step; and an X-ray CT measurement step of the cutting piece in which, using an X-ray CT apparatus, the gray level of the particles of the metal of interest contained in the cutting piece is measured with a higher resolution than that of the X-ray CT measurement of the solidified piece, and one or more of the three-dimensional position, three-dimensional shape, particle size, and bonding state of the particles of the metal of interest in the cutting piece is determined.

9. The method for analyzing ore according to claim 8, characterized in that, in the X-ray CT measurement step of the cut piece, two or more cut pieces are stacked and placed in an X-ray CT apparatus, the gray level of particles containing the metal of interest contained in the stacked cut pieces is measured, and one or more of the three-dimensional position, three-dimensional shape, particle size, and bonding state of particles containing the metal of interest contained in each stacked cut piece is determined.

10. The ore analysis method according to claim 8, comprising: a step of preparing a cross-section sample of particles containing the metal of interest from the cross-section based on one or more pieces of information on the three-dimensional position, three-dimensional shape, particle size, and bonding state of the particles containing the metal of interest in the cross-section; and a step of analyzing the cross-section sample using a SEM-EDS device to analyze one or more pieces of information on the shape of the particles containing the metal of interest, and the mating minerals to which they are bonded by single-edged and / or inclusion.

11. The method for analyzing ore according to any one of claims 1, 2, 6, 7, 8, 9, or 10, characterized in that the metal of interest is one or more metals selected from gold and the platinum group metals.

12. The method for analyzing ore according to claim 11, characterized in that the metal of interest is gold.

Images