rollingstone
starting to spend too much on rocks
Member since July 2009
Posts: 236
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Post by rollingstone on Feb 6, 2006 19:08:39 GMT -5
Quartzite is sandstone that has been changed by the heat and pressure of metamorphism so that the sand grains and silica cement are fused into a single mass. It looks kind of like quartz, but is opaque and a bit grainy. White and off-white are the most common colours, but iron oxides can give quartzite various red hues, and other impurities may produce other colours. I find that quartzite takes an okay but not spectacular polish. various polished pieces of quartzite: Only once have I ever found a small chunk that had mulitiple colours mixed together:
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Post by Alice on Feb 6, 2006 22:40:02 GMT -5
PolishedMOH - 7 Polished
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Post by texasrockhound on Feb 7, 2006 10:26:57 GMT -5
Hey Rollingstone -
I like 'em. Some look like they take a better shine than others...I've been wondering if Quartzite would tumble well 'cause I have an endless supply from my folks place in Central Texas...I like the white ones best...the ones I find are stain with Iron Oxides (just like yours!) which produce some nice colors and patterns....
Thanks for the Post!! Dan
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rollingstone
starting to spend too much on rocks
Member since July 2009
Posts: 236
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Post by rollingstone on Feb 15, 2006 17:33:30 GMT -5
Thought I'd add this pic of purple quartzite rough (dry):
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Post by entrerh9 on Apr 1, 2006 13:17:54 GMT -5
It was only recently that I learned that there are really two distinct kinds of quartzites, and that they are indistinguisahble without the aid of a microscope or a knowledge of where they came from. Both are equally tough and come in an array of colors. Both break through the quartz grains as well as around them.
Don described metaquartzite, which is a metamorphic rock formed just as he described. The other kind is orthoquartzite (also known as gannister or quartsite), where a fine grained, well-consolidated sandstone had silica-based cement coming out of water percolating through it and binding the sand grains together into a solid silica/quartz-like mass. Here in southcentral PA, for example, we have the Tuscarora orthoquartzite formation which forms the tops of our tallest ridges due to its extreme resistance to erosion.
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