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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.

Kentucky Agate
Kentucky Agate
Kentucky Agate


Mineral of the Month Archives

May 2007: Rainbow Fluorite

June 2007: Lake Superior Michipicoten Agate

July 2007: Labadorite

August 2007: Rain Flower Agate

Fall 2007: Malachite

December 2007: Nepheline Syenite

January 2008: Native Copper

February 2008: Amazonite

March 2008: Lake Superior Agate

April 2008: Shadow Agate

May 2008: Apohpylite

June 2008: Ocean Jasper

Summer 2008: Marra Mamba Tiger's Eye

September 2008: Mohawkite

October 2008: Mexican opal

November 2008: Prehnite

December 2008: Picture Jasper

January 2009: Sea Shell Jasper

February 2009: Polychrome Jasper

March 2009: Selenite Desert Rose

Spring 2009: Coyamito Agate

July 2009: Obsidian Needles

August 2009: Goethite

September 2009: Banded Iron Formation

Fall 2009: Fairburn Agate

March 2010: Fossilized Dinosaur Bone

April/May: 2010 Kentucky Agate

June 2010: Nantan Meteorite

July 2010: Mookaite Jasper

Aug/Sept 2010: Polyhedroid Agate

Fall 2010: Ammonite Fossil

September 2011: Petoskey Stones

Spring 2011: Petrfied Wood

Winter 2011: Argentina Condor Agate

January 2012: Mary Ellen Jasper

March 2012: Mexican Crazy Lace Agate

June 2012: Moqui Marbles

September 2012: Chlorastrolite Greenstone

March 2013: Jacobsville Sandstone

August 2013: Unakite

November 2013: Skip-an-Atom Agate

April 2014: Tiger's Eye

September 2014: Black Corundum

February 2015: Condor Agate

June 2015: Petoskey Stone

November 2015: Slag

June 2016: Lake Superior Copper Replacement Agates

March 2017: Chert

July 2017: Kona Dolomite

December 2017: Septarian Nodule

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Gitche Gumee Museum.
E21739 Brazel Street
Grand Marais, Michigan 49839


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