Areas with ellinaite in gehlenite-rankinite paralava (a–b), Hatrurim Basin, Israel. BSE and reflected light images. Symbols: Eln-1, Eln-2 – ellinaite; Po – Cr-rich pyrrhotite; Gh – gehlenite; Ran – rankinite; La – larnite–flamite; Prv – Si-rich perovskite; Alt – alteration products after pyrrhotite. The image is published in an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( https://creativecommons.org/licenses/by/4.0/ ). — Photo: Victor V. Sharygin, Sergey N. Britvin, Felix V. Kaminsky, Richard Wirth, Elena N. Nigmatulina, Grigory A. Yakovlev, Konstantin A. Novoselov, and Mikhail N. Murashko · CC BY 4.0
Rankinite
Rankinite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₃Si₂O₇.
It crystallizes in the monoclinic crystal system (space group P2_1/a).
Key properties: Mohs hardness 5.5; specific gravity 2.96–3; Vitreous luster; optically biaxial.
IMA symbol Rnk, grandfathered status — known before the IMA’s founding, named in 1942.
Found in high-temperature calc-silicate skarns.
It is found associated with Larnite, melilite, spurrite, kilchoanite, nagelschmidtite, gehlenite, cuspidine, monticellite, andradite, perovskite, magnetite.
The name refers to Dr. George Atwater Rankin (1884{?), physical chemist of the Geophysical Laboratory, Washington, D.C., USA, an early student of the system lime-alumina-silica.