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MINERAL OF THE MONTH

September 2014 - Black Corundum

Corundum is a crystalline form of aluminum oxide (Al2O3) with traces of iron, titanium and chromium. It can be found as a component in rocks as well as in pure crystal form. It is one of the naturally transparent materials, but can have different colors when impurities are present. Transparent specimens are used as gems -- Ruby and Sapphire. which are scientifically the same mineral but just different colors. Ruby is red and Sapphire is the variety that encompasses all other colors, although the most popular and valued color of Sapphire is blue.

Because of corundum's hardness (pure corundum is has a hardness of 9.0 Mohs), it can scratch almost every other mineral. It is commonly used as an abrasive on everything from sandpaper to large machines. Corundum is the third hardest natural mineral known to science. The hardest mineral, diamond is four times harder than corundum. The second hardest is Moissanite (Silicon Carbide) at 9.25. The hardness of corundum can be partially attributed to the strong and short oxygen-aluminum bonds. These bonds pull the oxygen and aluminum atoms close together, making the crystal not only hard but also quite dense for a mineral made up of two relatively light elements.

Corundum can be found in stream and beach sands because of its hardness and resistance to weathering. The largest documented single natural crystal of corundum ever found measures about 65×40×40 cm (26×16×16 in), and weighs 152 kg (335 lb).

Corundum can not only be artificially synthesized, but even natural gem stones are often heat treated to enhance their color.

The specimen featured in the picture above was acquired from Pierre Trudel, who recently visited the Gitche Gumee Museum from Quebec, Canada. The smaller specimen shown in close up detail below was donated by Pierre.

Below are a couple of close up photos that I took of this specimen of black corundum.

Metaphysical Properties

According to the web page http://www.mineralminers.com/html/corminfo.htm#metaphysical-corundum-information , “Corundum is said to enhance one's creativity, self-confidence, awareness, intuition and ambition. It is also said to help release negative emotions in constructive ways while giving give inner peace.”

CITES:


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

June 2012: Moqui Marbles

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

Winter 2011: Argentina Condor Agate

Spring 2011: Petrfied Wood

September 2011: Petoskey Stones

January 2012: Mary Ellen Jasper

March 2012: Mexican Crazy Lace Agate

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

August 2016: Puddingstone


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

 


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