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

pegmatite A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic co ...

s 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, macr ...

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 Elk P ...

South Dakota South Dakota (; Sioux language, Sioux: , ) is a U.S. state in the West North Central states, North Central region of the United States. It is also part of the Great Plains. South Dakota is named after the Lakota people, Lakota and Dakota peo ...

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 AmE, American and CanE, Canadian English) is a chemical element with the Symbol (chemistry), symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately o ...

. 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 discovere ...

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