MINERAL OF THE MONTH
November 2008: Prehnite
This yellow green mineral is found throughout the world, but most notably in Australia, South Africa, Germany, and the United States. The specimen featured this month was found in the Keeweenaw Peninsula in Michigan’s Upper Peninsula. It not only includes crystals of Prehnite, but also specs of copper, calcite, and silver. It forms near the surface of basaltic lava flows and often occurs in geodes or veins. It forms as a result of low grade metamorphism from hydrothermal solutions.
Prehnite can be confused with gyrolite, smithsonite, and hemimorphite. It can be distinguished because it is harder than these other three minerals. Smithsonite has more of a vitreous or pearly luster and hemimorphite is usually bluer in color while gyrolite is not as glassy.
Prehnite is a phyllosilicate of calcium and aluminium with the formula: Ca2Al(AlSi3O10)(OH)2. It is brittle with an uneven fracture and a slight vitreous luster with a white streak. It has a hardness of 6 to 6.5, with an average specific gravity of 2.80-2.90. It is translucent wth a color that varies from light green to grey, yellow, or white. When heated, this mineral gives up water but will not take the water back up when cooled.
Phrenite was first discovered in South Africa by Colonel Hendrik Von Prehn, an early Dutch governor of the Cape of Good Hope colony. It was the first mineral to be named after a person.
Its metaphysical properties are thought to enhance energy, provide protection, and promote calmness. It is also used to advance the state of meditation and help you to remember your dreams.
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
February 2010 Kentucky Agate
March 2010 Fossilized Dinosaur Bone
April/May 2010 Kentucky Agate
Copyright All rights reserved.
Gitche Gumee Museum.
E21739 Brazel Street
Grand Marais, Michigan 49839
