Lamproite (a source rock for diamonds)

Collection Highlights | Updated 3 days ago

Olivine lamproite in thin section (cross-polarized light) with crystals of olivine in a phlogopite-rich groundmass, Ellendale 9, West Kimberley Province. Field of view is 24 mm wide. Western Australian Museum specimen number WAM R5.2009.
Olivine lamproite in thin section (cross-polarized light) with crystals of olivine in a phlogopite-rich groundmass, Ellendale 9, West Kimberley Province. Field of view is 24 mm wide. Western Australian Museum specimen number WAM R5.2009.
WA Museum

Coloured diamonds are famously found in Western Australia’s Kimberley region. The Argyle mine has unearthed pink, purple and brown diamonds as well as very rare red and blue diamonds. The Ellendale mine was renowned for yellow diamonds. 

Most diamonds, including those mined at Argyle and Ellendale, were formed at high pressure, 140–250 kilometres below old, thick parts of the Earth’s crust. They remained deep for millions of years before travelling up to the surface in rushes of magma. 

Some exceptionally large and rare gem-quality diamonds crystallised from liquid metal, even deeper within the Earth’s mantle. 

Lamproite is one of the deepest-sourced volcanic rocks that occurs at the Earth’s surface. In the Kimberley region, rare lamproite magmas sampled diamond-bearing mantle rocks during their ascent to the surface. Their mantle mineral cargo included both diamonds and rounded olivine crystals called macrocrysts, as shown in this thin section image of lamproite from Ellendale in the west Kimberley.

Rock Collection