kirwanite

Kirwanite is a mineraloid, meaning it is a naturally occurring substance that resembles a mineral but lacks a definite crystalline structure. It is a hydrated phosphate mineral, primarily composed of rare earth elements. The chemical formula is typically represented as (REE,Ca,Na)5(PO4)3(OH,F)·nH2O, where REE signifies a mixture of rare earth elements.

Kirwanite was first described in 1975 and is named after William D. Kirwan, a prospector who discovered it in the Gold Butte district of Nevada, USA. The mineral is known for its vibrant colors, often appearing in shades of green, yellow, and orange, though colorless and white varieties also exist. Its appearance can be waxy or vitreous.

This mineraloid is found in association with other phosphate minerals and is typically formed under hydrothermal conditions. It is relatively rare and has not been found in extensive deposits, making it of interest primarily to mineral collectors and geologists studying rare earth element mineralization. Its geological significance lies in its contribution to understanding the complex geochemistry of rare earth element-bearing hydrothermal systems. Due to its amorphous nature, precise physical properties like hardness and specific gravity can vary.