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Types of Metamorphic Rocks

Metamorphic rocks are older rocks that were transformed by heat, pressure and fluids deep in the crust. Foliated types such as slate, phyllite, schist and gneiss show aligned minerals and banding; non-foliated types such as marble, quartzite and hornfels are massive and recrystallized.

Identify them by their sheen, banding, and the minerals that grew during metamorphism, such as garnet, mica, kyanite and staurolite.

Mohs hardness in this group runs from 1 to 7.5.

Also browse:Types of Igneous RocksTypes of Sedimentary RocksMinerals A to ZGemstonesMetals & Alloys

All metamorphic rocks (19)

Marble specimen: white and gray metamorphic rockMarbleMohs 3.5 · White streakUnakite specimen: pink and green mottled and salmon metamorphic rockUnakiteMohs 6.5 · Variable; test individual minerals streakSlate specimen: gray and black metamorphic rockSlateMohs 3.5 · Variable; test individual minerals streakAnthracite specimen: black and steel gray metamorphic rockAnthraciteMohs 2.5 · Black to dark gray streakAmphibolite specimen: black and dark green metamorphic rockAmphiboliteMohs 5.5 · Variable; usually pale gray to white streakGreenschist specimen: green and gray green metamorphic rockGreenschistMohs 4.5 · Variable; usually pale greenish gray streakHornfels specimen: gray and black metamorphic rockHornfelsMohs 6 · Variable; usually pale gray streakBlueschist specimen: blue and blue gray metamorphic rockBlueschistMohs 5.5 · Variable; usually pale gray streakSkarn specimen: green and brown metamorphic rockSkarnMohs 5.5 · Variable by mineral content streakMetaconglomerate specimen: gray and white metamorphic rockMetaconglomerateMohs 6.5 · Variable by pebbles and matrix streakMylonite specimen: gray and black metamorphic rockMyloniteMohs 5.5 · Variable by mineral content streakEclogite specimen: green (omphacite) and red (garnet) metamorphic rockEclogiteMohs 6–7.5 · Vitreous (garnet and omphacite grains)Gneiss specimen: gray and pink metamorphic rockGneissMohs 6–7 · Vitreous to glimmering (mica-rich bands)Migmatite specimen: pink and black and light and dark layered metamorphic rockMigmatiteMohs 5–7 · Vitreous to dull (banded)Phyllite specimen: silvery gray and greenish gray metamorphic rockPhylliteMohs 2.5–4 · Silky to satiny (sericite/chlorite sheen)Quartzite specimen: white and gray metamorphic rockQuartziteMohs 7 · Vitreous to sugary/granularSchist specimen: silver-gray and golden (mica-rich) metamorphic rockSchistMohs 2.5–7 · Vitreous to silky/glittery (mica-rich)Serpentinite specimen: green and dark green metamorphic rockSerpentiniteMohs 2.5–4 · White streakSoapstone specimen: gray and green metamorphic rockSoapstoneMohs 1–2.5 · White streak

Frequently asked questions

What are the most common metamorphic rocks?

The most searched metamorphic rocks in the StoneSnap database are Marble, Unakite, Slate, Anthracite, and Amphibolite.

How do you identify metamorphic rocks?

Start with luster and color, then bracket the Mohs hardness with a scratch test and check the streak on unglazed porcelain. Mohs hardness in this group runs from 1 to 7.5. Each entry below lists the diagnostic properties and its common look-alikes.

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