Unfading Red

Submitted by Raven Mueller on Wed, 2014-07-09 08:35
Stone Type (Commercial): 
Physical Data
Munsell Color(s): 
Stone Type (Lithologic): 
Grain Size: 
Very Fine
Petrographic Description: 

Specimen: 2014-034

This specimen is a red slate. The color of the slate is imparted by a high iron content that likely includes hematite and limonite. There are few identifiable crystal grains in this specimen. Quartz/feldspar grains are common 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 mostly .15 mm and less in length and show some orientation preference. There are ovoid inclusions that may represent remnant sedimentary features. These have a maximum dimension of .4 by .2 mm, a minimum of .1 by .05 mm, and a modal range around .3 by .2 mm. Most of these are filled with unidentifiable mica minerals. Hematitie, limonite and other opaque minerals often form envelopes around these structures. The preferential elongation of these structures does not correspond to the preference seen in mica minerals. Clearly relict sedimentary features are visible on macro-inspection of the slide in the form of banding. These features are visible under the microscope by the changing prevalence of light (quartz/feldspar) and reddish (opaques/iron hydroxides) minerals. 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.
7/16/14 MP


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Specimen ID
2014-034 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
2014-034 Specimen shown in non-polarized image Specimen shown in cross-polarized image


No quarry information available for this stone.

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