Braggite is a rare Pt-Pd-Ni sulfosalt and moncheite is a rare Pt-Pd-Te-Bi sulfosalt and are members of rare sulfosalt series. Specimens of any species are very uncommon from the obscure Stillwater Complex of Montana. This polished serpentine slab hosts both species in very rare combination. Splendent brassy braggite laths to about 3 mm are scattered on the sliced and polished serpentine matrix with silvery-bright amoeba-looking moncheite masses to about 1.0 cm. Ex. Josef Vajdak Collection. He was known as one of the top rarities dealers in such things in the second half of the 1900s. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Braggite
A dense, steel-grey platinum-palladium-nickel sulfide crystallizing in the tetragonal system.
Intro adapted from Wikipedia (CC BY-SA).
Braggite is an IMA-recognized mineral species in the sulfide class, with the chemical formula PtS.
It crystallizes in the tetragonal crystal system (space group P4_2/m).
Key properties: specific gravity 10; Metallic. Anisotropism: Distinct, in purplish and pinkish shades of gray and brown. R1 –R2: (400) 41.3–41.8 luster.
IMA symbol Bg, grandfathered status — known before the IMA’s founding, named in 1932.
Found in layered mafic intrusives, formed at high magmatic temperatures.
It is found associated with Sperrylite, cooperite, laurite, platinum (Potgietersrus district, South Africa); pentlandite, pyrrhotite, chalcopyrite, cubanite, nickelian mackinawite, gold.
The mineral was named to honor Sir William Henry Bragg (1862–1942) and Professor William Lawrence Bragg (1890–1971), Cambridge University, Cambridge, England.