Submitted by Raven Mueller on Wed, 2014-07-09 08:39
Stone Type (Commercial): 
Physical Data
Munsell Color(s): 
Stone Type (Lithologic): 
Grain Size: 
Very Fine
Petrographic Description: 

Specimen: 2013-007

This specimen is a gray slate. The color of the specimen suggests significant graphite dust presence. 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 common with a maximum dimension of .25 mm, most are smaller. Albite twinning is visible in a few feldspar grains. 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 mostly .12 mm and less in length. Visible mica crystals show some orientation preference. Carbonate minerals are common and occupy about 10 percent of slide area with a maximum crystal dimension of about .14 mm. A few carbonate crystals have rhombohedral edges, but most are anhedral. Clearly relict sedimentary features are visible on macro-inspection of the slide in the form of banding. These are also visible under the microscope as alternating dark and light areas that are mostly produced by the density of opaque minerals. These bands are composed of mostly hexagonal euhedral crystals .005 to .010 mm in size. 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
2013-007 No image available. Close-up image of specimen in dry conditions. Finish: Natural cleftdownload image

Thin Sections

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Specimen ID Non-polarized Cross-polarized
2013-007 Specimen shown in non-polarized image Specimen shown in cross-polarized image


NOTE: Quarry locations are approximate.

Vermont Structural Slate Quarry
620 Saltis Rd
05764 Poultney , Vermont
United States
43° 33' 42.876" N, 73° 14' 7.26" W
Vermont US

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