Benstonite on calcite from Hardin County (State unknown). Held in the A. E. Seaman Mineral Museum . — Photo: Chris857 · CC BY-SA 3.0
Benstonite
A barium-calcium-magnesium carbonate described in 1961 and named for Orlando Benston.
Intro adapted from Wikipedia (CC BY-SA).
Benstonite is an IMA-recognized mineral species in the carbonate class, with the chemical formula Ba₆Ca₆Mg(CO₃)₁₃.
It crystallizes in the hexagonal crystal system (space group R-3).
Key properties: Mohs hardness 3–4; specific gravity 3.6–3.66; refractive index 1.611; optically uniaxial.
IMA symbol Ben, IMA status: approved, named in 1961.
Found in a barite deposit (Magnet Cove, Arkansas, USA); in Alpine veins cutting a carbonatite (Bayan Obo deposit, China).
It is found associated with Barite, calcite, quartz (Magnet Cove, Arkansas, USA); calcite, alstonite, fluorite, sphalerite (Cave-in-Rock, Illinois, USA); huntite, barytocalcite.
The mineral was named to honor Orlando J. Benston (1901–1966), metallurgist for the Baroid Division, National Lead Co., Malvern, Arkansas, USA, who supplied the first specimens.