Segelerite is a complex

phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phosph ...

mineral with formula Ca Mg Fe³⁺ O H( PO₄)₂· H₂O. It occurs in pegmatites and forms striking green or chartreuse

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...

s. It was discovered in 1974 in the

Black Hills The Black Hills ( lkt, Ȟe Sápa; chy, Moʼȯhta-voʼhonáaeva; hid, awaxaawi shiibisha) is an isolated mountain range rising from the Great Plains of North America in western South Dakota and extending into Wyoming, United States. Black ...

South Dakota South Dakota (; Sioux: , ) is a U.S. state in the North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota and Dakota Sioux Native American tribes, who comprise a large porti ...

by an amateur mineralogist from New York, Curt G. Segeler (1901–1989), after whom it is named. It is closely related to ''overite'' which is virtually the same mineral except that the iron is replaced by

aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...

. Another mineral in the same series is ''juonniite'' wherein the iron is also replaced, this time by

scandium Scandium is a chemical element with the symbol Sc and atomic number 21. It is a silvery-white metallic d-block element. Historically, it has been classified as a rare-earth element, together with yttrium and the Lanthanides. It was discovered in ...

References

Webmineral.com - SegeleriteHandbook of Mineralogy - Segelerite
Calcium minerals Magnesium minerals Iron(III) minerals Phosphate minerals Orthorhombic minerals Minerals in space group 61 {{Phosphate-mineral-stub