Siderite, Sphalerite
Aggenys Mine, Northern Cape Province, South Africa
Small Cabinet, 7.5 x 6.6 x 4.5 cm
A fine specimen from a small find that was brought out at Munich in 2006. These very unusual, barrel-shaped crystals are actually epimorphs, i.e. casts after calcite crystals, which have been dissolved away. The striking large crystal is 4.0 cm tall and is complete-all-around. The two major crystals are pristine. Microprobe analysis in South Africa by Bruce Cairncross and others shows that the shimmering, metallic-like coating is a mixture of siderite and sphalerite. The piece is very light weight for its size and, in fact, the casts are hollow, as the one broken crystal on the side reveals.