Sheldrickite
A sodium-calcium carbonate-fluoride named for George Sheldrick, creator of the SHELX crystallography software.
Intro adapted from Wikipedia (CC BY-SA).
Sheldrickite is an IMA-recognized mineral species in the carbonate class, with the chemical formula NaCa₃(CO₃)₂F₃·H₂O.
It crystallizes in the hexagonal crystal system (space group P3_2).
Key properties: Mohs hardness 3; specific gravity 2.86; White streak; Vitreous to silky luster; optically uniaxial.
IMA symbol Sdk, IMA status: approved, named in 1996.
A very rare late-stage hydrothermal mineral in a marble xenolith in nepheline syenite in association with an intrusive alkalic gabbro-syenite complex.
It is found associated with Shortite, pectolite, microcline, polylithionite, arfvedsonite, molybdenite.
The mineral was named to honor Professor George M. Sheldrick (1942–), Institute for Organic Chemistry, University of Göttingen, Göttingen, Germany.