When you first see a kimberlite, you may not think much of it. In fact, many Kansas kimberlites do not stand out to the untrained eye. But, underneath their quiet forms are pipe like formations that reach deep into the earth and bring volcanic substances to the surface.
This is what the Kansas Geological Society has to say about kimberlites:
“With rare exceptions, the rocks we see at the surface in Kansas are sedimentary in origin—that is, they’re made up of particles deposited by wind or water. Among the exceptions are the kimberlites of Riley and Marshall counties, igneous rocks formed from the cooling of molten magma that exploded to the surface during the Cretaceous Period, about 90 million years ago.
Kimberlite is a soft, dull-gray rock with thin white veins that originates deep in the earth, in the upper mantle—the layer that lies about 25 to 250 miles beneath the earth’s surface. As kimberlitic magma erupts, it expands, breaking up rock in its path and exploding through the crust (perhaps at speeds of 1,300 feet per second). These eruptions form deep, carrot-shaped pipes that often occur in small clusters. The explosion produces small craters at the surface and leaves behind a mixture of igneous and sedimentary rock that often contains garnets, a dark-red, semi-precious stone.” [http://www.kgs.ku.edu/Publications/GeoRecord/2000/vol6.1/Page1.html]
Diamonds are brought to the surface via kimberlites. Unfortunately, no diamonds have been found in any Kansas kimberlite. However, other gemstones have been found occasionally.
Kimberlites exist throughout the United States, mainly in the Appalachian Mountain Range. New kimberlites are being discovered regularly. In Kansas, the majority of the kimberlites that have been discovered are in Riley and Marshall Counties. All of the kimberlites in Kansas are on private property.
Because kimberlites are made of igneous rocks, they have a different magnetic signature than the surrounding sedimentary rocks. Using this and other knowledge, geologists are able to find new kimberlite pipes.
When looking for kimberlites in Kansas, keep in mind each kimberlite is usually not that much taller than the surrounding landscape. The Bala kimblerlite is only 15 feet high, but 200 feet in diameter. The Stockdale kimberlite is only one of five that forms a topographic low, that is, its caldera is sunken.
To claim a smiley face [find], please email the answers to the questions below. If you’d like, post a picture in your log with the kimberlite in the distance.
Why would you need to know about kimberlites as a geocacher?
What feature, besides height, makes the kimberlite stand out?
Do you think any gemstones have been found in this particular kimberlite?