Seeing a Kimberlite Pipe: A Mine Tunnel
The best way to see a kimberlite pipe is first hand, like a miner or geologists, in the tunnels that provide access to the pipe in an underground mine. The tunnel recreated in the exhibition goes from the local bedrock, through a boundary zone that is extremely fragmented, and into the kimberlite, with its inclusions of mantle rocks and diamonds.
In tunnels that contain a kimberlite pipe, you might be able to see the following:
Shattering of local bedrock and combination with kimberlite
in the boundary zone: This shows that the eruption
was extremely violent, volatile in its early stages.
Mica: In addition to mica, the tunnel contains calcite, which is unseen. Large proportions of these two minerals are strange in an igneous rock. There is water in mica and carbon dioxide in calcite, instead of abundant gas (steam and carbon dioxide) dissolved in the magma. The gases bubbled out of the magma and propelled the cruel eruption -- like uncorking a bottle of hot champagne.
Round and sharp pieces of rocks in the kimberlite: These are xenoliths, accurately foreign rocks in the kimberlite. They were dislodged from Earth's layer by the rising magma. These rare samples are expensive to geologists studying Earth's interior and the origin of diamonds.
Red garnets and a diamond: Both minerals are established in kimberlites and in some of the xenoliths. Certain garnets may show the presence of diamonds.
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