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July 2007: Labadorite


This month’s mineral of the month is Labradorite, which was first discovered in the Labrador Peninsula in Canada. It is also found in Norway, Finland, and Russia. It is truly a captivating mineral that displays a colorful shiller effect when held and moved during observation. The color display is from layers of intergrowth inside the crystal. These intergrowth layers are caused from compatible chemistries at high temperature becoming incompatible at lower temperature that results in a separating and layering of the crystal components. The color effect is caused when light enters the specimen, only to be refracted back and forth by the deeper layers. The refracted light is slowed as it travels through the layers and mixes with other light rays to change and produce a different wavelength of light. The color effect depends on the thickness and orientation of the layers.

Labradorite is a member of the plagioclase series of minerals, which comprises feldspars. It contains sodium, calcium, aluminum, silicon, and oxygen. The color is gray to smoky black. It has a dull to vitreous luster. The crystals are transparent to translucent. It has a conchoidal fracture pattern, a hardness of between 6 and 6.5, and a specific gravity of between 2.70 and 2.74. The flashes of color (labradorescence) can vary between blue, violet, green and sometimes orange and yellow.

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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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