Redbird - Pershing County Nevada, USA — Photo: Pacific Museum of Earth from Canada · CC BY-SA 2.0
Robinsonite
Robinsonite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula Pb₄Sb₆S₁₃.
It crystallizes in the monoclinic crystal system (space group I2/m).
Key properties: Mohs hardness 2.5–3; specific gravity 5.64–5.75; Metallic. Anisotropism: Strong; in blue-gray, cream-white, and brown-gray. R1 –R2: n.d luster.
IMA symbol Rob, grandfathered status — known before the IMA’s founding, named in 1952.
A primary hydrothermal mineral with other lead sulfosalts.
It is found associated with Zinkenite, boulangerite, semseyite, plagionite, stibnite, sphalerite, galena, pyrite, quartz, calcite.
The mineral was named to honor Dr. Stephen Clive Robinson (1911–1981), Geological Survey of Canada, who first synthesized the mineral at Queen’s University, Kingston, Ontario, Canada.