White crystal aggregates of the rare borate mineral teepleite. From: Tecopa Hot Springs, Tecopa, Inyo County, California, United States of America. — Photo: David Hospital · CC BY-SA 4.0
Teepleite
Teepleite is an IMA-recognized mineral species in the halide class, with the chemical formula Na₂B(OH)₄Cl.
It crystallizes in the tetragonal crystal system (space group P4/nmm).
Key properties: Mohs hardness 3–3.5; specific gravity 2.076; Vitreous to greasy, dulled on exposure to air luster; optically uniaxial.
IMA symbol Tee, grandfathered status — known before the IMA’s founding, named in 1939.
Formed by reaction of boron-rich brines with halite in an extremely desiccated lake (Borax Lake, California, USA).
It is found associated with Halite, trona, burkeite, hanksite.
The mineral was named to honor John Edgar Teeple (1874–1931), for his work on the chemistry of Searles Lake, California, USA.