Prior to the discovery of the Talnakh sperrylite specimens, the only significant sperrylite crystals known were a very small number collected in the 1920s from a now-exhausted occurrence on the Tweefontein Farm in South Africa (Spencer, 1926; Cairncross and Dixon, 1995; Wilson, this issue), and some lesser crystals from the type locality at Sudbury, Ontario (Wells, 1889; Penfield, 1889; Walker, 1895; Goldschmidt and Nicol, 1903).
The minerals occur as metacrystals, veinlets and polymineralic intergrowths of sperrylite [PtAs.sub.2], the atokite-rustenburgite series [(Pd,Pt).sub.3] Sn, paolovite [Pd.sub.2]Sn, and domains of [Pd.sub.2](Sn,As), [Pd.sub.5] [As.sub.2] and [(Pd,Ni).sub.5][As.sub.2].
Until the discovery of large, well-formed sperrylite crystals at the Oktyabrsky mine in the Norilsk region of Siberia in the mid-1980s, the Tweefontein farm in the Transvaal, South Africa, was the undisputed premier locality for the species.
It is known today as the world's third largest deposit of platinum-group elements, and it is here that some of the largest and finest sperrylite crystals ever seen were discovered.
They can reach 5 cm, and even the biggest ones remain razor-edged, mirror-faced, and possessed of such brilliant tin-white metallic luster as to suggest Russian sperrylite
The majority of the platinum (90-95%) in disseminated ore is found as sperrylite, with 1.2 ppm in pyrrhotite and pentlandite.
Platinum massive ores occur as sperrylite in pyrrhotite ores and as tetraferroplatinum, rustenburgite, maslovite and moncheite.
crystals (modified cubes) to 1.3 cm in matrix ...
Occurrence: Associated minerals are: ruthenium, isoferroplatinum, cherepanovite, rhodian irarsite, honshiite, sperrylite
, tulameenite, and unnamed IrAsTe.
Back again in the KARP room we find the show's only offering (that I noticed) of significant numbers of sperrylite
specimens from the now-famous locality of Talnakh, near Noril'sk, Siberia.
Wendell has, to put it mildly, a good aesthetic eye, and thus the viewer's own eye lingers long on practically every piece, and the longer the lingering, the better seems the specimen in question: for instance, his Mexican ludlamite, Russian sperrylite
, Afghanistan lazurite, Yukon lazulite, Russian pyrochlore, Sweet Home mine rhodochrosite .
Visitors should also look for one of the world's finest sperrylites
(from Russia--Mineralogical Record cover, vol.