Inyoite , Meyerhofferite Locality: Monte Azul deposit, Sijes, Salta , Argentina ( Locality at mindat.org ) Size: 5.7 x 4.1 x 3.1 cm. A razor-sharp crystal, to 3.5 cm on edge, and extremely impressive in person! One of my favorite miniatures here, this one LOOKS like it has a different crystal form almost, because of the sharp angular nature of its rhombohedral crystals, elongated steeply in one direction. A few gemmy, discrete Meyerhofferite crystals are included inside. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Meyerhofferite
A hydrated calcium borate formed mainly by the alteration of inyoite.
Intro adapted from Wikipedia (CC BY-SA).
Meyerhofferite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula CaB₃O₃(OH)₅·H₂O.
It crystallizes in the triclinic crystal system (space group P-1).
Key properties: Mohs hardness 2; specific gravity 2.12; Vitreous to silky luster; optically biaxial.
IMA symbol Mhf, grandfathered status — known before the IMA’s founding, named in 1914.
Typically a minor component of sedimentary or lake-bed borate deposits.
It is found associated with Inyoite, colemanite, hydroboracite, ulexite.
The mineral was named to honor Professor Wilhelm Meyerhoffer (1864–1906), German chemist, who first synthesized the compound.