硒辉锑银矿——一个新变种

SELENIAN MIARGYRITE--A NEW VARIETY OF MIARGYITE

硒辉锑银矿是辉锑银矿的一个新变种,为国内外首次发现。产于云南省哀牢山变质带西带的金矿区含金石英脉中。矿物呈粒状,粒径0.1—0.02mm;黑色,不透明,金属光泽;在显微镜下呈浅灰微蓝色,反射多色性弱,非均质性清楚;硬度117—141kg/mm^2,理论密度5.59g/cm^3;单斜晶系,空间群C2/c,a_0=1.3031(10)nm,b_0=0.4444(3)nm,c_0=1.3377(9)nm,β=98.19°(6),Z=8。

Selenian miargyrite is a new variety of miargyrite. It was first found in goldbearing quartz veins in middle-lower Silurian quartzite of the Ailaoshan metamorphic belt, Yunnan province. It is intimately associated with freibergite, stibnite, ullmannite and native gold. The mineral occurs as grains from 0.1 to 0.02mm in diameter. Black in colour,opaque and luster metallic. The colour of reflection is light grey with a faint blue tint. Its pleochroism is weak and the anisotropism is strong. Hv=117—141kg/mm^2,density (calculated) 5.90g/cm^3. X-ray study has shown that it is monoclinic, space group C2/c with α_0=1.3031(10)nm, b_0=0.4444(3)nm, c_0=1.3377(9)nm, α=98.19°(6) and Z=8. Chemical analysis has given 33.95—30.79 Ag, 40.30—39.18 Sb, 14.55—11.63 Se and 15.49—12.08 S. The ideal formula is Ag Sb (Se_(0·6)S_(1·4))_2.