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Zinkenite
A steel-gray lead-antimony sulfosalt forming dense clusters of needles — a 'feather ore' described in 1826.
Intro adapted from Wikipedia (CC BY-SA).
Zinkenite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula Pb₉Sb₂₂S₄₂.
It crystallizes in the hexagonal crystal system (space group P6_3).
Key properties: Mohs hardness 3–3.5; specific gravity 5.33; Steel-gray streak; Metallic. Anisotropism: Distinct. R1 –R2: (400) 39.1–44.2, (420) 39.2–44.4, (440) 39.3–44.6, (460) 39.2–44.5 luster.
IMA symbol Zkn, grandfathered status — known before the IMA’s founding, named in 1826.
A constituent of hydrothermal veins, in association with base metal and tin sulfides and sulfosalts.
It is found associated with Stibnite, jamesonite, boulangerite, bournonite, plagionite, fülöppite, cassiterite, stannite, andorite, pyrite, sphalerite, chalcopyrite, arsenopyrite, galena.
The name refers to J.K.L. Zinken (sometimes Zincken) (1798–1862), German mineralogist and mining geologist.