Semi-Weathering Gray-Green

Submitted by Raven Mueller on Tue, 2014-07-08 10:09
Stone Type (Commercial): 
Physical Data
Munsell Color(s): 
Stone Type (Lithologic): 
Grain Size: 
Very Fine
Petrographic Description: 

Specimen: 2014-008

This specimen is a gray-green slate. The color of the specimen possibly suggests the presence of graphite dust and chlorite. Owning to the aphanitic nature of the material, many of the constituent minerals in this specimen cannot be identified through microscopy. Quartz/feldspar grains are rare with a maximum dimension of .1 mm, most are smaller. Various species of mica presumably form the majority of the specimen’s fabric, but these are generally too small to be individually perceived. Identifiable crystals of mica are .05 mm and less in length and show some orientation preference. Carbonate minerals occupy approximately 5 to 10 percent of slide area with a maximum crystal dimension of about .08 mm. Most carbonate crystals have rhombohedral edges. Opaque minerals are rare and make up less than 1 percent of slide area. Clearly relict sedimentary features are not visible on macro-inspection of the slide or under the microscope. Overall the lack of more significant grain elongation and orientation prevalence indicates very low grade metamorphism. This may be due to the slide’s orientation, which is perpendicular to the likely direction of maximum tectonic stress.

7/14/15 MP


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Specimen ID
2014-008 Image of specimen in dry conditions. Finish: Natural cleftdownload image Close-up image of specimen in dry conditions. Finish: download image

Thin Sections

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Specimen ID Non-polarized Cross-polarized
2014-008 Specimen shown in non-polarized image Specimen shown in cross-polarized image


No quarry information available for this stone.

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