Metamorphic Rocks

Metamorphic rocks are formed when heat or pressure substantially changes some other type of rock. Both the texture and the chemical composition of the original rock can be changed significantly.

One common type of metamorphism is re-crystallization into much larger crystals. These are usually hard and often shiny and are prized as gemstones.

In some cases, increasing temperature and pressure will continue to transform metamorphic rocks into new forms. Thus shale or mudstone will first transform into slate. Under higher temperature and pressure, slates transform into schist which, in turn, will transform into gneiss.

  
Main Types of Metamorphic Rock

PARENT ROCK METAMORPHIC ROCK
slate or mudstone Slate
Schist
Gneiss
basalt or gabbro Amphibolite
quartz sandstone, siltstone or chert Quartzite
limestone or dolostone Marble

 

Slate Gneiss Quartzite
 
 

Rock specimens now available (at eBay):

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Queensland Boulder Opal Specimen

AU $65.00 (0 Bids)
End Date: Tuesday Mar-3-2020 17:17:11 EST
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Andamooka And Coober Pedy Opal Rough All Pieces Have Color

AU $45.00 (0 Bids)
End Date: Friday Mar-6-2020 14:02:13 EST
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SHUNGITE 2 x ELITE NOBLE FOR WATER PURIFICATION

AU $120.00 (0 Bids)
End Date: Monday Mar-2-2020 21:20:12 EST
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Andamooka Natural Opal Matrix Rough Specimen

AU $50.00 (0 Bids)
End Date: Thursday Mar-5-2020 17:23:06 EST
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Andamooka And Coober Pedy Opal Rough All Pieces Have Color

AU $45.00 (1 Bid)
End Date: Thursday Mar-5-2020 16:49:44 EST
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Fluorite on Quartz Second Soviet Mine Dal'negorsk Russia

AU $30.00 (0 Bids)
End Date: Friday Feb-28-2020 19:53:40 EST
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Fluorite on Quartz with Pyrite Yaogangxian Mine, Hunan province, China

AU $25.00 (0 Bids)
End Date: Friday Feb-28-2020 19:53:26 EST
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