Idsteinite

Idsteinite is a rare mineral with the chemical formula (Fe,Zn)2(AsO4)(OH). It was first discovered in the Idstein district of Hesse, Germany, in 1845, and is named after this location. Idsteinite is typically found in hydrothermal veins and is associated with other arsenic-bearing minerals such as olivenite and scorodite. It is a secondary mineral, formed through the oxidation of primary arsenic-bearing minerals.

Idsteinite crystals are usually small, ranging from a few millimeters to a few centimeters in size. They are typically dark brown to black in color, with a metallic luster. The mineral has a hardness of 3.5 to 4 on the Mohs scale and a specific gravity of approximately 4.2. It is orthorhombic in crystal system and belongs to the space group Pnma.

Idsteinite is of limited interest to collectors due to its rarity and small crystal size. However, it is sometimes used as a source of arsenic, which has various industrial applications. The mineral is also of interest to mineralogists due to its unique chemical composition and association with other arsenic-bearing minerals.