amminien

Amminien is a rare and historically significant mineral that belongs to the class of phosphates. It is characterized by its chemical composition of lead arsenate hydroxide, represented as Pb₂(AsO₄)(OH). The mineral typically forms as a secondary product in the oxidation zone of lead and arsenic-bearing ore deposits, often associated with minerals like cerussite, anglesite, and mimetite.

Amminien was first described in 1845 from specimens found in the mines of the Harz Mountains in Germany, particularly from the Rammelsberg deposit. Its name derives from the Latinized form of the German word *Ammoniak*, meaning ammonia, due to its early association with ammonium compounds in some analyses, though this is no longer considered accurate. The mineral is generally found in small, tabular or prismatic crystals, often exhibiting a yellowish to brownish hue.

Amminien is of interest to mineralogists and collectors due to its scarcity and distinctive appearance. It is typically found in low concentrations and is often overshadowed by more common minerals in its host environments. The mineral’s formation is linked to the alteration of primary lead and arsenic minerals under surface conditions, where oxidation and hydration processes play a key role.

While amminien is not economically significant, its occurrence provides insights into the geochemical processes affecting lead and arsenic deposits. Specimens are occasionally encountered in mineral collections, particularly from classic mining districts in Europe and other regions with historical lead mining activity. Its study contributes to the broader understanding of secondary mineral formation in ore deposits.