Natural Sphalerite Cluster Crystal from Bulgaria 101g

A steep, roughly pyramidal cluster of sphalerite crystals with a notably strong luster, the faces glassy to almost adamantine and dark enough to look black in most light. Turn the piece and the picture changes: along thin edges and around the crystal margins the sphalerite lights up in warm honey-brown and deep amber, showing the resinous color that lies under the black. Olive-yellow tarnish films run between some of the crystals, a broad brassy chalcopyrite crystal with striated faces sits on the lower right, and small bright silver galena patches appear on the reverse.

Sphalerite is zinc sulfide, and its color depends on how much iron sits in the structure: crystals with more iron are black, those with less are amber to green. This one falls at the dark end but still shows the amber wherever light gets through. From the Bulgarian lead-zinc veins of the Rhodope Mountains. Untreated. At 3.5 to 4 on the Mohs scale it is a soft mineral, and the 49mm size makes it easy to shelve in a display cabinet.

Natural sphalerite cluster, Bulgaria, single piece.