Montroydite and mercury from the Socrates Mine, Somona County, California, USA — Photo: Kritzolina · CC BY-SA 4.0
Montroydite
Natural mercury(II) oxide — a rare red-to-black mineral from the Terlingua mercury district of Texas.
Intro adapted from Wikipedia (CC BY-SA).
Montroydite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula HgO.
It crystallizes in the orthorhombic crystal system (space group Pnma).
Key properties: Mohs hardness 2.5; specific gravity 11.23; Yellow-brown streak; Vitreous to adamantine luster; optically biaxial.
IMA symbol Mtyd, grandfathered status — known before the IMA’s founding, named in 1903.
Found in hydrothermal mercury deposits.
It is found associated with Mercury, cinnabar, metacinnabar, calomel, eglestonite, terlinguaite, mosesite, kleinite, edgarbaileyite, gypsum, calcite, dolomite.
The mineral was named to honor Montroyd Sharp, an owner of the mercury deposit at Terlingua, Texas, USA.