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Wisconsin Red Granite

Submitted by Intern on Tue, 2015-03-10 10:34
Stone Type (Commercial): 
Availability: 
Available
Geology
Stone Type (Lithologic): 
Grain Shape: 
Angular
Grain Size: 
Coarse
Petrographic Description: 

Specimen: 2014-085-1
This sample is a plutonic rock dominated by mostly anhedral quartz and feldspar. The crystalline structure is coarse. Maximum crystal dimension is 4.8 mm (feldspar). There are two clear modes, one are the original, and larger, crystals that formed from the plutonic melt, which are mostly 2 to 1 mm in size. The other mode is the result of grain nucleation of quartz caused by tectonic stress. The modal size of these grains is around .08 mm. These stress induced grains surround most quartz grains and in some cases have completely replaced parent grains. Wave extinction is ubiquitous in larger quartz grains. Polysynthetic is the predominant form of feldspar twinning observed, some with visible curving, reflecting tectonic stress. Relative amounts of quartz and feldspar are difficult to estimate due to visual similarity, but feldspar predominates. Microperthitic texture is common in feldspars. Accessory minerals are relatively rare and comprise only about 5 percent of slide area. Biotite is the most common accessory mineral and is often altered to chlorite. Opaques are also present at less than 1 percent of slide area. Smectite and iron oxides and hydroxides occur in small cracks, particularly in feldspars. Feldspar grains generally have a dusty appearance, reflecting incipient alteration, but sericitization is minimal.
MP 9/4/2015

Specimen: 2014-085-2
This sample is a plutonic rock dominated by mostly anhedral quartz and feldspar. The crystalline structure is coarse. Maximum crystal dimension is 5.2 mm (feldspar). There are two clear modes, one are the original, and larger, crystals that formed from the plutonic melt, which are mostly 3 to 1 mm in size. The other mode is the result of grain nucleation of quartz caused by tectonic stress. The modal size of these grains is around .08 mm. These stress induced grains surround most quartz grains and in some cases have completely replaced parent grains. Wave extinction is ubiquitous in larger quartz grains. Carlsbad twinning is the most evident but polysynthetic twins are also present. Relative amounts of quartz and feldspar are difficult to estimate due to visual similarity, but feldspar predominates. Microperthitic texture is very common. Fracturing of feldspars from tectonic stress is evident. Accessory minerals are relatively rare and comprise only about 5 to 10 percent of slide area. Biotite is the most common accessory mineral and is often altered to chlorite. Opaques are also present at less than 1 percent of slide area. Smectite and iron oxides and hydroxides occur in small cracks, particularly in feldspars and in association with mafic minerals. There are a few alteromorphs of amphiboles that have now been almost completely replaced with alteration minerals. Feldspar grains generally have a dusty appearance, reflecting incipient alteration, but sericitization is minimal.
MP 9/4/2015

Images

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Specimen ID
2014-085-1 Image of specimen in dry conditions. Finish: download image
2014-085-2 Image of specimen in dry conditions. Finish: download image

Thin Sections

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Specimen ID Non-polarized Cross-polarized
2014-085-1 Specimen shown in non-polarized light.download image Specimen shown in cross-polarized light.download image
2014-085-2 Specimen shown in non-polarized light.download image Specimen shown in cross-polarized light.download image

Quarry

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