furanoidit

Furanoidit is a rare mineral species, classified as a phosphate mineral. It was first discovered in 1997 in the Furano mine, Hokkaido, Japan, from which it derives its name. The mineral is typically found in association with other phosphate minerals such as wavellite and variscite.

Furanoidit crystallizes in the monoclinic system and is characterized by its distinctive prismatic crystals. It is usually colorless or white, but can also exhibit shades of yellow or brown due to impurities. The mineral has a hardness of approximately 3.5 on the Mohs scale and a specific gravity of around 2.8 to 3.0.

The chemical formula of furanoidit is (Na,Ca)2(Fe,Al)2(PO4)2(OH)2. It is a sodium-calcium iron-aluminum phosphate hydroxide, belonging to the autunite group of minerals. The mineral's structure consists of phosphate tetrahedra linked to octahedra of iron and aluminum, with sodium and calcium ions occupying the interstices.

Furanoidit is of limited geological interest due to its rarity and the specific conditions required for its formation. However, it is valued by mineral collectors for its unique crystal habit and association with other phosphate minerals. The mineral's discovery and characterization have contributed to the understanding of the complex mineralogy of the Furano mine and similar phosphate-rich environments.