Pecoraite Locality: Culver-Baer Mine (Culver-Baer Quicksilver Mine; Buckman Mine), North Fork Little Sulphur Creek, Cloverdale, West Mayacmas Mining District, Sonoma County, California, USA Green aggregates of pecoraite, probably pseudomorph. Field of view 2 cm. Specimen and photo Leon Hupperichs. — Photo: Leon Hupperichs · CC BY-SA 3.0
Pecoraite
A nickel serpentine-group silicate named for USGS director William Pecora — an apple-green mineral of nickel laterites.
Intro adapted from Wikipedia (CC BY-SA).
Pecoraite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ni₃Si₂O₅(OH)₄.
It is a member of the Serpentine, Clay structural group.
Key properties: specific gravity 3.084; Vitreous luster; optically biaxial.
IMA symbol Pco, IMA status: approved, named in 1969.
Formed by weathering of Ni-Fe meteorite fragments in a desert environment (Wolf Creek meteorite); along shears in Archaean ultramafic rocks (Otway prospect, Western Australia); in geodes (St. Louis, Missouri, USA).
It is found associated with Maghemite, quartz, goethite, cassidyite, reevesite (Wolf Creek meteorite); millerite, gasp¶eite, otwayite, nullaginite (Otway prospect, Western Australia).
The mineral was named to honor Dr. William Thomas Pecora (1913–1972), Director of the U.S. Geological Survey, geologist and student of nickel silicate deposits.