White acicular crystals of the very rare mineral mattheddleite from the most famous locality for the mineral, Caldbeck Fells (Caldbeck Fells, Cumbria, United Kingdom) where it is first identified. See Min Record. 22:105-121 for a review on the discovery. Ex-Renato Pagano collection. — Photo: David Hospital · CC BY-SA 4.0
Mattheddleite
Mattheddleite is an IMA-recognized mineral species in the silicate class, with the chemical formula Pb₅(SiO₄)₁.₅(SO₄)₁.₅Cl.
It crystallizes in the hexagonal crystal system (space group P6_3/m). It is a member of the Apatite structural group.
Key properties: specific gravity 6.96; White streak; Adamantine luster; optically uniaxial.
IMA symbol Mhd, IMA status: approved, named in 1985.
Lining cavities in quartz which contain other oxidized lead minerals.
It is found associated with Lanarkite, cerussite, anglesite, pyromorphite, hydrocerussite, caledonite, leadhillite, susannite, macphersonite.
The name refers to Matthew Forster Heddle (1828–1897), Scottish mineralogist.