Name: Gray Quartzite
Type: rock
Class: Metamorphic
Subclass: Quartzite
Particle Size: Fine
Sample No.: qrtzit5
Owner: JHU
Wavelength Range: All
Origin: Sample No. 382, The Hunt and Salisbury Collection at the U.S.Geological Survey, Denver, Co.
Collection Date: N/A
Description: This is a sample much like the previous one in composition.  It is a fine-grained slightly metamorphosed well-compacted sandstone with some secondary quartz deposition, and much more silica/chalcedony deposition.  The quartz grains, unlike the previous rock, show evidence of only weak strain and fewer fluid inclusions.  In addition there are scattered detrital green and brown tourmaline and zircon. Particle size was 0-75 Micrometer.   Original ASTER Spectral Library name was jhu.becknic.rock.metamorphic.quartzite.fine.qrtzit5.spectrum.txt
Presumably the gray color results from tiny opaque inclusions in the cores of 
some of the quartz grains.  Modal analyses gave 82.4% quartz, 16.4% 
chalcedony, 0.5% tourmaline, 0.4% zircon, 0.16% opaques, 0.11% 
clay/alteration. 
