crednerite

Crednerite is a rare mineral with the chemical formula (Fe,Zn)3(AsO4)2·8H2O. It is named after the German mineralogist Karl Friedrich Credner, who first described the mineral in 1845. Crednerite is typically found in the oxidized zones of arsenic-bearing hydrothermal deposits, often associated with other secondary arsenic minerals such as scorodite and olivenite. It forms as a result of the alteration of primary arsenic-bearing sulfides, such as arsenopyrite, in the presence of oxygen and water.

The mineral is characterized by its pale yellow to yellowish-brown color, which can sometimes exhibit a reddish tint due to the presence of iron. Crednerite has a hardness of approximately 2.5 on the Mohs scale and a specific gravity of around 3.2. It typically occurs as botryoidal, crust-like aggregates or as radiating fibrous masses. The mineral is not considered to be of significant economic importance, but it is of interest to mineral collectors and researchers due to its rarity and unique chemical composition.

Crednerite's crystal structure is monoclinic, and it belongs to the space group P21/c. The mineral's name is derived from the Greek words "krednos," meaning "hidden," and "lithos," meaning "stone," reflecting its rarity and the fact that it was initially overlooked by mineralogists. Despite its rarity, crednerite remains an important subject of study for geologists and mineralogists, as it provides valuable insights into the processes of arsenic mineralization and the alteration of hydrothermal deposits.