Tetrahedrite, (Cu,Fe)12Sb4S13 (copper antimony sulfide), is named for its common crystal form, the tetrahedron. Tetrahedrite is in an informal group of minerals — Photo: Darla Sondrol · CC0
Linarite
A lead-copper sulfate famous among collectors for its intense, saturated azure-blue crystals.
Intro adapted from Wikipedia (CC BY-SA).
Linarite is an IMA-recognized mineral species in the sulfate class, with the chemical formula CuPb(SO₄)(OH)₂.
It crystallizes in the monoclinic crystal system (space group P2_1/m). It is a member of the Linarite structural group.
Key properties: Mohs hardness 2.5; specific gravity 5.35; typically blue; Pale blue streak; Vitreous to subadamantine luster; refractive index 1.835; optically biaxial.
IMA symbol Lna, grandfathered status — known before the IMA’s founding, named in 1822.
Occurs as an uncommon secondary mineral in the oxidized zone of Pb–Cu deposits.
It is found associated with Brochantite, anglesite, caledonite, leadhillite, cerussite, malachite, hemimorphite.
The name refers to its occurrence at Linares, Spain.
Collections: Collector Favorites, Rare & Remarkable.