Memsseedite

Memsseedite is a rare, naturally occurring mineral that was first discovered in the Mems mine in the Democratic Republic of the Congo. It is named after the mine where it was found, and its chemical composition is (Fe,Mn)2(AsO4)(SO4)(OH)2·6H2O. Memsseedite crystallizes in the monoclinic crystal system and typically forms prismatic crystals or granular aggregates. It is often associated with other minerals such as olivenite, mimetite, and wulfenite.

The mineral exhibits a bright yellow to orange color, which is characteristic of its iron and manganese content. Its hardness on the Mohs scale is approximately 2.5, making it relatively soft. Memsseedite is also known for its distinctive yellow fluorescence under ultraviolet light, which is a useful diagnostic feature in mineral identification.

The mineral's formation is thought to be related to the oxidation of arsenic-bearing minerals in the presence of sulfuric acid, a process that is common in the oxidation zones of hydrothermal deposits. Memsseedite is of interest to mineral collectors and researchers due to its rarity and unique properties. However, it is not considered to have any significant economic value.