Crystallization behavior of platinum minerals within Pt-Sb-Bi bearing ore magmas and mineralogical properties of the existing minerals were investigated at 1,000℃ by synthetic experiment. High purity reagents were used as starting materials and silica tubings as containers. Reaction products were analysed by reflecting microscopy, X-ray diffraction, electron probe microanalysis, and micro-hardness test. Stable minerals at 1,000℃ are platinum, electron probe microanalysis, and micro-hardness test. Stable minerals at 1,000℃ are platinum, stump-flite (PtSb) and geversite (PtSb2). They are in equilibrium with liquid (ore magma). Platinum contains considerable amount of Sb of 7.5 at.%, whereas Bi only up to 0.9 at.%. Pure stumpflite is hexagonal with space group P63/mmc, and unit cell parameters are a=4.1318(6), c=5.483(1)a. VHN50=417(2)a. Geversite has cubic structure with space group Pa3. Cell parameters are a=6.4373(2)a and Vicker hardness values VHN50=663.5 (566~766). Both stumpflite and geversite show solid solution and their end-members are Pt48.8Sb40.7-Bi10.5, and Pt33.7-Sb59.8Bi6.5, respectively. Although stumpflite (m.p. 1,043℃) and unnamed PtBi (m.p. 765℃) do not form a complete solid solution at 1,000℃, they are known, at 600℃, to form a continuous solid solution. Geversit (m.p. 1,226℃) also forms complete solid solution with insizwaite (m.p. 660℃). Unit cell dimensions of the minerals above increases with the amount of Bi substituting for Sb.

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