|Torbernite from Margabal mine, Aveyron, Midi-Pyrenees, France.|
Torbernite is the mineral from hell. The prism shaped green crystals form as secondary deposits in granitic rocks, and are composed of uranium. Formed through a complex reaction between phosphorous, copper, water and uranium, the stunning crystal displays have seduced many mineral collectors into taking a sample for a shelf collection. If the uranium decay from a pocket sized Chernobyl were not enough, lethal radon gas capable of causing lung cancer slowly releases from these hot rocks. This is one crystal to leave alone. Torbernite can occur in granite, so your stone countertop just might contain traces of torbernite. The bright green crystal blooms were used by prospectors as indicators of uranium deposits.