Aphthitalite

Aphthitalite is a rare mineral, specifically a phosphate mineral, with the chemical formula Ca2Mn3+(PO4)2(OH)3. It was first discovered in 1845 in the Aphthitalis mine in the Greek island of Cephalonia. The mineral is named after this mine, which is derived from the Greek word "aphthitalis," meaning "causing ulcers," a reference to the mineral's historical use in treating ulcers.

Aphthitalite typically forms as a secondary mineral in the oxidation zone of manganese-rich deposits. It is often found in association with other manganese minerals such as rhodochrosite, pyrolusite, and psilomelane. The mineral is characterized by its dark brown to black color, which is due to the presence of manganese in its structure. It has a hardness of 4.5 on the Mohs scale and a specific gravity of approximately 3.7.

Aphthitalite is of limited economic importance due to its rarity and the fact that it is not a significant source of manganese or phosphorus. However, it is of interest to mineral collectors and researchers due to its unique chemical composition and the conditions under which it forms. The mineral's occurrence in the oxidation zone of manganese deposits provides valuable insights into the geochemical processes that occur in these environments.