cestodit

Cestodit is a mineral belonging to the phosphate group. It is chemically known as calcium magnesium phosphate, with the formula CaMg(PO4)2. Cestodit is an iron-free end-member of the merrillite group, which is a solid solution series. It was first discovered in the Kola Peninsula, Russia, and named after the Russian mineralogist K. A. Vlasov, whose given name was Cestod, by the Russian Academy of Sciences in 1975.

The mineral typically occurs as a secondary mineral in phosphate deposits. It is often found in association with other phosphate minerals such as apatite and crandallite. Cestodit crystallizes in the monoclinic crystal system and has a vitreous luster. Its color can range from white to gray. It is relatively soft, with a Mohs hardness of around 4 to 5.

Cestodit has been identified in various geological settings, including pegmatites and sedimentary rocks. Its formation is generally attributed to the alteration of primary phosphate minerals. While not a common mineral, it is of interest to mineralogists for its crystallographic properties and its place within the merrillite group.