A
precious metal alloy mainly including a
quaternary alloy of Pt, Au, Ni, and Pd includes 7.5% by atom or more and 72.5% by atom or less of Pt, 5.5% by atom or more and 62.5% by atom or less of Au, 3% by atom or more and 62.5% by atom or less of Ni, and 0.15% by atom or more and 38% by atom or less of Pd. When respective concentrations (% by atom) of Pt, Au, Ni, and Pd represent CPt, CAu, CNi, CPd, the value of the following first compositional parameter z1 is 0.5 or more and 2.88 or less and also the concentration CPd of Pd satisfies CPd≤z2 with respect to the following second compositional parameter z2. A present inventive
precious metal alloy is a high-
hardness precious metal alloy to which a strengthening mechanism by
spinodal decomposition and / or ordering is applied.z1=(CPt×CAu×CNi) / 10000[Expression 1]z2=a×(CAu)3+b×(CAu)2+c×CAu+d[Expression 2]coefficients a, b, c, and d are the following numerical values.a=0.00077, b=−0.102,c=3.607, d=1.722