Premier Mine (Cullinan Mine), Cullinan, Pretoria, Gauteng Province, South Africa

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A diamond mine in a kimberlite pipe, dated 1200 million years old, owned by De Beers. With a cross section of 32 ha at surface, the pipe is the largest ever found in South Africa. It was discovered around 1900 as a consequence of prospecting for heavy minerals in nearby rivers, where diamonds were found and traced back to their source in the hills at Cullinan, 20-25 miles east of Pretoria. The mine started producing in 1903 and was operated as an open-pit mine until 1932, when it had to close due to the eceonomic depression. In 1950, it was re-started as an underground mine and has been operating continuously since then. In 2005, it produced 1.3 million cts from 4.6 million tons of ore. The workings are 2,900 feet by 1,400 feet across and more than 700 feet deep.

Premier mine is famous for its large diamonds. The world's largest diamond, the 3106 ct Cullinan was discovered in 1905. Recent notable stones were the 599 ct "Centenary "and the 1083 ct "Unknown Brown". The diamond grade increases with depth, possibly as a result of diminishing proportions of country-rock inclusions. Among researchers, the mine is best known for its mantle-derived rocks and minerals, of which the garnet harzburgites and lherzolites have received most attention.

Mineral List

Actinolite Apophyllite-(KF) Calcite

Diamond Diopside Forsterite

'Garnet' Graphite Ilmenite

Prehnite Pyrite Spinel

12 entries listed. 11 valid minerals.

References