Brown sharp crystals of the extremely rare mercury mineral gianellaite from the type locality: Mariposa Mine, Terlingua District, Brewster County, Texas, United States of America. Gianellaite in crystals is very very rare. The species has only been found in two localities worldwide. Analyzed specimen. — Photo: David Hospital · CC BY-SA 4.0
Gianellaite
Gianellaite is an IMA-recognized mineral species in the sulfate class, with the chemical formula (Hg₂N)₂(SO₄)(H₂O)ₓ.
It crystallizes in the cubic crystal system (space group F-43m).
Key properties: Mohs hardness 3; specific gravity 7.19; [Vitreous.] luster.
IMA symbol Gia, IMA status: approved, named in 1972.
A rare secondary mineral coating fracture surfaces in oxidized portions of a hydrothermal mercury deposit, the nitrogen likely derived from decaying organic matter (Mariposa mine, Texas, USA).
It is found associated with Cinnabar, terlinguaite, montroydite, mercury, calomel, hematite, calcite (Mariposa mine, Texas, USA).
The mineral was named to honor Professor Vincent Paul Gianella (1886–1983), Head of the Department of Geology, MacKay School of Mines, University of Nevada, Reno, Nevada, USA.