Unfading Mottled Purple and Green

Submitted by Raven Mueller on Wed, 2014-07-09 08:46
Stone Type (Commercial): 
Physical Data
Munsell Color(s): 
Stone Type (Lithologic): 
Grain Size: 
Very Fine
Petrographic Description: 

Specimen: 2013-011

This specimen is a pink and green mottled slate. The color of the specimen suggests significant chlorite and iron presence and possibly variable oxidation environments in the original sedimentary environment. Owning to the aphanitic nature of the material, many of the constituent minerals in this specimen cannot be identified through microscopy. Visible Quartz/feldspar grains are relatively rare with a maximum dimension of .08 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 mostly .15 mm and less in length. Visible mica crystals show moderate orientation preference. Carbonate minerals occupy about 10 percent of slide area with a maximum crystal dimension of about .25 mm. Most carbonate crystals have rhombohedral edges. A few exceptional carbonate crystals occur in compromise boundary masses in what were likely void spaces that allowed the precipitation of secondary minerals. Carbonate minerals in these spaces have a maximum dimension of .24 mm. Minimal relict sedimentary features are visible on macro-inspection of the slide in the form of pink-green mottling. These are difficult to discern under the microscope and appear only in ppl as slight color differences. 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
2013-011 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
2013-011 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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