Cerussite, Matlockite Locality: Cromford, Matlock, Derbyshire, England, UK (Locality at mindat.org) Size: small cabinet, 6.9 x 5.2 x 3.7 cm Matlockite on Ceruss — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Matlockite
Lead fluoride-chloride — namesake of the matlockite group, discovered in a mine near Matlock, Derbyshire.
Intro adapted from Wikipedia (CC BY-SA).
Matlockite is an IMA-recognized mineral species in the halide class, with the chemical formula PbClF.
It crystallizes in the tetragonal crystal system (space group P4/nmm). It is a member of the Matlockite structural group.
Key properties: Mohs hardness 2.5–3; specific gravity 7.12; typically yellow or green; white streak; Adamantine, pearly on {001} luster; refractive index 2.096; optically uniaxial.
IMA symbol Mtl, grandfathered status — known before the IMA’s founding, named in 1851.
Found in the oxide zone of some lead-bearing mineral deposits.
It is found associated with Phosgenite, anglesite, cerussite, galena, sphalerite, barite, fluorite (Cromford, England); diaboleite, boleite, caledonite, leadhillite (Tiger, Arizona, USA).
The name refers to the first occurrence near Matlock, England.
Collections: Rare & Remarkable, Collector Favorites.