islander
off to a rocking start
Member since May 2020
Posts: 15
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Post by islander on Mar 31, 2021 15:45:41 GMT -5
If you put a picture of the rock on here then people might be able to help you with a general identification. In summary, a sedimentary rock may have bedding planes and will have a grain although the size of grain can vary considerably. A metamorphic rock is a rock that has been altered by contact heat from a local igneous intrusion (contact metamorphism - an example of this is marble which is a metamorphosed limestone) or by immense heat and pressure at depth (regional metamorphism - an example of this would be gneiss).
All of the colours in rocks are caused by the elements the minerals they're formed from contain. The vast majority of red rocks and minerals contain iron oxide although there are exceptions (cinnibar is an ore of mercury and is red, realgar is a sulfide of arsenic and is also red...)
The sparkles could be mica flakes.
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Sabre52
Cave Dweller
Me and my gal, Rosie
Member since August 2005
Posts: 20,487
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Post by Sabre52 on Mar 31, 2021 22:26:50 GMT -5
Metamorphic rocks can have both layers and bands of various minerals caused by high pressure during metamorphism. Therefore, not all rocks showing bands or layers are sedimentary. Igneous rocks tend to be uniform in texture and not have bands or layers. Oddly, the agates we love so much, while formed in sedimentary and igneous rocks, are nether sedimentary, metamorphic or igneous but rather silica that has been deposited in voids.
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Post by stephan on Apr 1, 2021 9:42:35 GMT -5
Pink can also come from manganese, such as in rhodonite and rhodochrosite.
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