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June 2016 - Lake Superior Copper Replacement Agates

This web page update features the copper replacement agate. They can only be found in the Keweenaw Peninsula, located in Michigan’s Upper Peninsula. They can be found in the mine dumps near abandoned copper mines from the Kearsarge Lode. Most of these agates are small – less than an inch in diameter. They are extremely rare and difficult to find, usually requiring labor intensive work to free them from the basalt matrix rock. These agates are well sought after because of their rarity, their interesting patterns, and the vast array of other mineral inclusions. In addition to copper these agates often have other mineral inclusions including silver, calcite, malachite, tenorite, epidote, and pumpellyite, In most cases these small agates are fully husked, requiring them to be cut to expose their inner beauty.

The copper replacement agate shown below includes malachite, pumpellyite, and epidote inclusions.

The agate below has white chalcedony bands on the left and clear calcite on the right. Copper is in the outer shell, surrounding the specimen. The green is epidote and the red is a copper oxide.

The two photos below show copper replacement agate nodules in basalt matrix rock. In addition to copper there is also prehnite, epidote, and pumpellyite (dark green inclusions). These photos were taken by Dave Schuder.

The specimen shown below has basaltic matrix on the left and copper replacement on the right. The copper bands alternate with the chalcedony bands. This photo is from my agate book, Agates Inside Out.

CITATION: The first three photos shown above (used with permission) are from the Wayne W. Sukow collection http://www.sukowssuperiorminerals.com.


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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