clausthalite

Clausthalite is a rare mineral composed of lead selenide, with the chemical formula PbSe. It belongs to the sulfide-arsenide-antimonide group and crystallizes in the cubic system, often forming small, granular masses or cubic crystals. Its color typically ranges from steel-gray to black, and it possesses a metallic luster. Clausthalite is relatively soft, with a Mohs hardness of around 2.5 to 3, and a high specific gravity.

This mineral is found in hydrothermal vein deposits and is often associated with other selenium-bearing minerals, as well as quartz, calcite, and various metallic sulfides. Notable occurrences have been reported in Clausthal-Zellerfeld, Germany (from which it derives its name), as well as in Sweden, Canada, and the United States. Due to its rarity and the scarcity of selenium deposits, clausthalite is not a significant ore of lead or selenium, but it is of interest to mineral collectors and geologists studying the distribution of selenium in the Earth's crust. Its chemical composition and crystal structure make it a member of the small group of minerals that are selenides of metals.