A surface covering unit comprises x primary elements, wherein x is an integer equal to or greater than 1. Each primary element is a rotational tessellation having a plural pairs of sides extending in a generally radial direction from plural vertices, respectively. In each pair, the two sides are rotationally spaced by an angle of 60, 90, 120 or 180 degrees, and each side is substantially a rotational image of the other side. The sum of the plural vertices angles is 180, 240, 270, 300 or 360 degrees. Preferably, all of the sides are irregularly shaped, but one or more sides could be wholly or partially straight. Optionally, one or more edges of each unit are marked with indicia to facilitate matching
mating sides of adjacent units. A wide variety of units may be constructed having different numbers and arrangements of primary elements. As all the units are combinations of primary elements, they readily mate with each other. A surface covering comprises a multiplicity of surface covering units assembled to form a continuous surface without overlap between units and without substantial gaps between units. Because of the irregular side configurations, and different sizes and shapes of individual units, one can construct a continuous surface that has a natural, random and apparent custom appearance. Optionally, minor surface and edges variations are made from unit to unit to further enhance the natural appearance of the surface covering.