MINERAL OF THE MONTH: April/May 2010 – Kentucky Agate

The mineral of the month is Kentucky agate. It became the state stone for Kentucky in 2000. This agate is quite unique in its coloration. It most typically has bands of yellow, black, and gray. Occasionally there are sections of blue, red, pink, or orange. This distinctive agate was formed in shale and siltstone in the Borden layer of the Mississippian geologic period between 225 and 375 million years ago. They can be found in Estill, Jackson, Lee, and Powell counties. Hunters find them most often in the Buck, White Oak, and Middle Fork Creeks. Due to the hilly terrain, rains cause the creeks to rise sometimes 10 or 15 feet, depending on the location. The rushing water washes the agate nodules out of the sedimentary layers. Since most Kentucky agates have thick husks, successful hunters use a rock hammer or other metal object to hit the rocks in the river. The silica rocks have a “ping” sound, as compared to other river rocks that have more of a “thud” sound. Not all silica rocks found in the creeks are agate, however. There are also silicified fossils, geodes, and quartz balls.

The photos included in this update were taken by Tom Shearer. These are three of the photos from the new agate book Please see the gift shop section of this web page for more information about the new agate book.


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