Platy pale green crystals of the extremely rare nickel mineral theophrastite from the famous Lord Brassey mine (Heazlewood District, Tasmania, Australia), known for its paragenesis of nickel minerals. Ex- collection Chris Deroo and ex-collection Rik Dillen. — Photo: David Hospital · CC BY-SA 4.0
Theophrastite
The rare mineral form of nickel(II) hydroxide — lime-green crystals named for the philosopher Theophrastus.
Intro adapted from Wikipedia (CC BY-SA).
Theophrastite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Ni(OH)₂.
It crystallizes in the hexagonal crystal system (space group P-3m1). It is a member of the Brucite structural group.
Key properties: Mohs hardness 3.5; specific gravity 4; Pale green streak; Vitreous luster; optically uniaxial.
IMA symbol Tph, IMA status: approved, named in 1980.
Occurs as coatings in chromitite in lenses in serpentinites (Vermion district, Greece); on chromitite (Hagdale quarry, Scotland).
It is found associated with Magnetite, chromite, millerite, vesuvianite, chlorite, andradite-grossular, nickeliferous serpentine minerals, calcite (Vermion district, Greece); zaratite.
The name refers to Theophrastus, (ca. 371 BC-ca. 287 BC), the first Greek mineralogist.