Deposit types/Diamonds

Kimberlite and lamproite pipe

Carrot-shaped pipes of volcanic breccia that carry diamonds up from the mantle.

What it is

Carrot-shaped pipes of volcanic breccia that carry diamonds up from the mantle.1

How it forms

Kimberlite or lamproite magma climbs fast from the mantle along deep fractures, quenches and fills a pipe (diatreme) with breccia. Diamonds are scattered through it as crystals picked up on the way. Pipes weather quickly into hollows.1

Host rocks

Kimberlite diatreme breccia; olivine and leucite lamproite.1

Where it forms

Ancient stable cratons, often along major basement fractures or domed areas; not tied to mountain building.1

How old

Most productive pipes about 80 to 100, 250 and 1,000 to 1,100 Ma1

Typical grade

Mined kimberlites yield 0.1 to 0.6 ppm diamond1

How geologists look for it

Indicator minerals in soil and stream sediment (pyrope garnet, magnesian ilmenite, phlogopite, chromium and nickel anomalies); lamproite pipes lack ilmenite.1

Mines of this type

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Mines

An example ofKimberley Big HoleSee Kimberley Big Hole, an example of this deposit type.1An example ofJagersfontein diamond mineSee Jagersfontein diamond mine, an example of this deposit type.1An example ofVenetiaSee Venetia, an example of this deposit type.1An example ofOrapaSee Orapa, an example of this deposit type.1An example ofJwanengSee Jwaneng, an example of this deposit type.1An example ofMir diamond mineSee Mir diamond mine, an example of this deposit type.1An example ofUdachnaya pipe (Udachny mine)See Udachnaya pipe (Udachny mine), an example of this deposit type.1An example ofArgyle diamond mineSee Argyle diamond mine, an example of this deposit type.1An example ofCatocaSee Catoca, an example of this deposit type.1An example ofEkatiSee Ekati, an example of this deposit type.1An example ofDiavikSee Diavik, an example of this deposit type.1

Sources

  1. Mineral Deposit Models (Bulletin 1693, Cox and Singer, eds., 1986) US Geological Survey

From the Prospector Trails mining history dataset: each fact links to the source it was checked against. Figures are as the source gives them, in the money of their day. Not investment advice.

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Cover photos from Wikimedia Commons: Super Pit, Kalgoorlie by Kgbo, CC BY-SA 4.0; Draglines by Roy Luck, CC BY 2.0.