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Prehnite

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Title: Prehnite
Medium: Digital Photography
Photographer: Aaron J. Greenblatt
Camera Type: Panasonic DMC-LZ7 Lumix 7.2 MP
Editing: Edited in PhotoShop 7.0 for color accuracy, size, and to apply copyright and border.

Location: Photograph taken at the 2008 Southeastern Michigan Gem and Mineral Show at the Southgate Civic Center in Southgate, Michigan. Show hosted by the Midwest Mineralogical & Lapidary Society.

Description: Sitting in a white cardboard box on a dealer's table was this five-inch-wide light green cluster of prehnite crystals from Westfield, Massachusetts. This piece was selling for $75 and would have made for a nice cabinet specimen - though admittedly the price was a bit high. This picture really doesn't do this specimen any justice.

About Prehnite: Prehnite (Calcium Aluminum Silicate Hydroxide) has the chemical formula: Ca2Al(AlSi3O10)(OH)2. It crystallizes in the orthorhombic crystal system. Prehnite is brittle with an uneven fracture and a vitreous to pearly luster. Its Mohs hardness is 6-6.5, its specific gravity is 2.80-2.90 and its color varies from light green to blue or white. It is also translucent.

Like zeolites (which are silicates consisting of interlocking tetrahedrons of silicon oxides and aluminum oxides), prehnite can give off water when heated, but it can not gain the water back like zeolites do. This is because prehnite is not a zeolite, but a member of the phyllosilicates subclass - which includes minerals such as serpentine, talc, apophyllite, chrysocolla, and gyrolite. Members of this group are often the last to chemically break down in erosional and weathering processes and thus they constitute a significant amount of the soils and fine grained sedimentary rocks that most people encounter.

Information Sources:
[link] (wiki - Prehnite)
[link] (galleries - Prehnite)
[link] (galleries - The Phyllosilicate Subclass)
[link] (galleries - Zeolites)

Legal: Copyright © Aaron J. Greenblatt. All rights reserved. Commercial use prohibited. This image and commentary may not be used for any reason without expressed written consent.


Please click here to view my photography work located in my Gallery.

Please click here for images of my glass work located in my other Gallery.

Please click here for images of my glass studio located in my other Scraps.
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Comments5
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ghashogh's avatar
very beautiful, very very beautiful mineral ,
i like to know it's chemical activity in the different types of soils.