horsite

Horsite is a rare and unusual mineral that was first discovered in 1979 in the Horse Creek area of the U.S. state of Utah. It is named for its type locality, Horse Creek. The mineral is a complex phosphate of calcium, magnesium, and iron, with the chemical formula CaMgFe(PO4)2. Horsite crystallizes in the monoclinic system and typically forms prismatic crystals or granular masses. It is usually colorless or white, but can also be found in shades of yellow, brown, or gray due to impurities.

Horsite is relatively soft, with a Mohs hardness of 4.5 to 5. It has a specific gravity of approximately 3.2 and is non-fluorescent. The mineral is transparent to translucent and has a vitreous to pearly luster. Horsite is often found in association with other phosphate minerals such as apatite, fluorapatite, and triphylite.

Due to its rarity and the fact that it is not a commercially valuable mineral, horsite is not widely collected or studied. However, it is of interest to mineralogists and collectors who are interested in rare and unusual minerals. The Horse Creek area, where horsite was first discovered, is a well-known locality for a variety of minerals, including other phosphate minerals and rare earth elements.