I had the opportunity to visit the Kimberlite deposits and diamond mine that are in the eastern part of Elliott County with a group of seventh graders.

Diamonds are often found in Kimberlite.
Kimberlite is formed as semi liquid magma from deep in the earth's mantle forces its way up through the mantle and then the crust.  As it moves through the rocks above it chunks break off and are mixed in.  The first picture shows the dark black/grey Kimberlite and several lighter colored inclusions (xenoliths).   Other minerals are formed from the elements found in the mantle.  The other pictures show a piece of translucent yellow/brown/green olivine and a bit of dark brown/black mica that are common in this Kimberlite.  Other minerals that have been found include: garnet, tourmaline, hornblende, magnetite, ilmenite, chromite, titanite, rutile, actinolite, staurolite, quartz, feldspar, zircon, topaz, monazite, xenotime, and fluorite.
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In Arkansas at the Crater of Diamonds State Park you can still find diamonds that were left in the soil formed by the breakdown of Kimberlite.
And of course Kimberlite is named from the famous diamond bearing deposits in South Africa where most of the world's diamonds are mined.
Unfortunately according to the University of Kentucky no diamonds have ever been authenticated from the Elliott County deposits.
But several people have told me of friends or relatives that found diamonds ranging in size from a walnut to a fist.

Here is some of the equipment left by the Kentucky Kimberly Diamond Company which operated here starting in 1906.
The mining operation started with excavated rock and soil being passed through a crusher of which only the foundation remains.

The crushed rock and soil were then mixed with water in the device pictured below to make it easy to separate the very fine material from the rest.
   

The resulting slurry was then passed through the screening box where it is separated into course, fine, and very fine fractions.
   

Today the output from the screening process would be passed through an X-ray fluorescence sorting process to separate the diamonds from residual waste.
Back then the sorting was done by hand.

As they came to the site the students had high hopes of finding a diamond that would make them rich.

They set to work sifting through the gravel along the stream bed. Some waded right in.
      

While none of the students found diamonds (not that they told me about anyway) they all learned a bit of the history of the county and a bit of geology.
What they did find were Garnets.  Most found a few, one student found 9 another 15.
Here are three that were found in the stream.
   

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