Siderite, Sphalerite
Aggenys Mine, Northern Cape Province, South Africa
Cabinet, 12.4 x 8.2 x 3.0 cm
A dramatic and showy cabinet 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. 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 right reveals.