Bayerite
One of the natural forms of aluminium hydroxide, Al(OH)₃ — a component of bauxite and a polymorph of gibbsite.
Intro adapted from Wikipedia (CC BY-SA).
Bayerite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Al(OH)₃.
It crystallizes in the monoclinic crystal system (space group P2_1/a).
Key properties: specific gravity 2.53; optically biaxial.
IMA symbol Byr, grandfathered status — known before the IMA’s founding, named in 1928.
Probably precipitated from high-aluminum gels on carbonates at pH > 5.8 (Hatrurim Formation, Israel); as weathered crusts on amphiboles and pyroxenes (Dnieper region, Russia); in bauxites.
It is found associated with Calcite, gypsum, portlandite, ettringite, vaterite, thaumasite (Hatrurim Formation, Israel).
The artificial compound is thought to have been named for the 19th-century German metallurgist Karl J. Bayer; the name was then applied to the natural mineral.