Minerals & Rocks: Metamorphic

Metamorphic rocks result from the subjection of a protolithic parent rock (igneous, sedimentary, or metamorphic) to heat and/or pressure and/or chemically active fluids. Metamorphic rocks are classified according to the parent rock and the degree of deformation to which the rocks have been subjected. Metamorphism occurs locally (contact) or on a large scale (regional).

Sedimentary rock Metamorphic product (low to high grade)
Conglomerate

Meta-conglomerate, schist, gneiss

Breccia Meta-breccia, schist, gneiss
Sandstone Quartzite, mica schist
Shale/siltstone/claystone Phyllite, slate, schist, gneiss, "fubarite"
Limestone/dolostone Marble (color shows "argillaceous" or "carboniferous")
Black shale Black slate
Peat/coal Anthracite through graphite with or without associated natural gas, petroleum and asphalt; Mississippi-type lead and zinc deposits

Chemical metamorphic rocks:

CompositionMineral NameRock Name/Ore
Au Gold Gold Ore
Ag Silver Silver Ore
Cu Copper Copper Ore
Pt PlatinumPlatinum Ore
S Sulfur Native Sulfur
CaF2FluoriteFluorospar

Deposition of metals results from regional metamorphism, volcanism, hydrothermal vents, and sulphide solutions:

CompositionMineral NameRock Name/Ore
PbSGalenaLead
ZnSSphaleriteZinc
FeS2Pyrite/MarcasiteIron
(Cu,Fe)S2ChalcopyriteCopper

Solutions of hot water chemically alter carbonates and silicates:

CompositionMineral NameRock Name
SiO2 transparent...Quartz, rock crystal
SiO2 translucent...Jasper, flint, chert, quartz, chalchedony, agate, silicified fossils, petrified wood
CaCO3CalciteTravertine marble, geodes, stalactites/stalagmites

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