Diamond Mine Tunnel

Diamond...
.... mine tunnel.

The best way to see a kimberlite pipe is first hand, like a miner or geologist, 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 highly fragmented, and into the kimberlite, with its inclusions of mantle rocks and diamonds.

In a tunnel that contained a kimberlite pipe, you might be able to see the following:

Shattering of local bedrock and mixing with kimberlite in the boundary zone: This shows that the eruption was extremely violent, explosive in its early stages.

Mica: In addition to mica, the tunnel contains calcite, which is invisible. Large proportions of these two minerals are unusual in an igneous rock. There is water in mica and carbon dioxide in calcite, representing abundant gas (steam and carbon dioxide) dissolved in the magma. The gases bubbled out of the magma and propelled the violent eruption -- like uncorking a bottle of hot champagne.

Round and angular pieces of rocks in the kimberlite: These are xenoliths, literally foreign rocks in the kimberlite. They were dislodged from Earth's mantle by the rising magma. These rare samples are valuable to geologists studying Earth's interior and the origin of diamonds. You can learn more about this in the room off of the tunnel.

Red garnets and a diamond: Both minerals are found in kimberlites and in some of the xenoliths. Certain garnets may indicate the presence of diamonds.