Marrite , Galena Locality: Lengenbach Quarry , Im Feld (Imfeld; Feld; Fäld), Binn Valley, Wallis (Valais) , Switzerland ( Locality at mindat.org ) Size: 4.1 x 2.2 x 1.9 cm. A validated specimen of this very rare silver-lead-arsenic sulfide species from Lengenbach. Mark exchanged it from Dr. Jaroslav Hyrsl who in turn obtained it in trade from the Natural History Museum in Bern, Switzerland, in about 1995. Although microcrystalline, the specimen has some display value - more than most such. The two arrows point to the marrite microcrystals (one or two at each arrow). The rest is galena. The marrite is dull on the surface, as opposed to the galena, which is bright. From the type locality. Ex. Dr. Mark Feinglos Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Marrite
A lead-silver-arsenic sulfosalt — the arsenic counterpart of freieslebenite.
Intro adapted from Wikipedia (CC BY-SA).
Marrite is an IMA-recognized mineral species in the sulfosalt class, with the chemical formula AgPbAsS₃.
It crystallizes in the monoclinic crystal system (space group P2_1/a).
Key properties: Mohs hardness 3; specific gravity 5.822; Metallic. Anisotropism: Distinct, strong in oil. R1 –R2: n.d luster.
IMA symbol Mrr, grandfathered status — known before the IMA’s founding, named in 1905.
Of hydrothermal origin, in dolostone.
It is found associated with Lengenbachite, rathite, tennantite, sartorite.
In honor of Dr. John Edward Marr (1857–1933), Professor of Geology, Cambridge University, Cambridge, England.