BETA

Mottled Gray-Black

Submitted by Raven Mueller on Tue, 2014-07-08 09:57
Stone Type (Commercial): 
Availability: 
Available
Physical Data
Color: 
Munsell Color(s): 
Geology
Stone Type (Lithologic): 
Grain Size: 
Fine
Very Fine
Petrographic Description: 

Specimen: 2014-005

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 .16 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 .03 mm and less in length. Visible mica crystals show some orientation preference. Carbonate minerals are common and occupy approximately 15 percent of slide area with a maximum crystal dimension of about .12 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 largely reflective of opaque mineral presence. Opaque minerals overall make up less than 5 percent of slide area. 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

Images

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Specimen ID
2014-005 Image of specimen in dry conditions. Finish: Natural cleftdownload image Close-up image of specimen in dry conditions. Finish: Natural cleftdownload image

Thin Sections

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Specimen ID Non-polarized Cross-polarized
2014-005 Specimen shown in non-polarized light.download image Specimen shown in cross-polarized light.download image

Quarry

NOTE: Quarry locations are approximate.

Fair Haven Quarry
Fair Haven , Vermont
United States
43° 35' 18.5316" N, 73° 14' 54.6" W
Vermont US

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