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Amphibolite is a non-foliated metamorphic

rock that forms through recrystallization underconditions of high viscosity and directedpressure. It is composed primarily of amphiboleand plagioclase, usually with very little quartz.The specimen shown above is about two inches(five centimeters) across.

AMPHIBOLITE

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Gneiss is foliated metamorphic rock that has abanded appearance and is made up of granularmineral grains. It typically contains abundantquartz or feldspar minerals. The specimenshown above is about two inches (fivecentimeters) across.

GNEISS

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Hornfels is a fine-grained nonfoliatedmetamorphic rock with no specific composition.It is produced by contact metamorphism.Hornfels is a rock that was "baked" while neara heat source such as a magma chamber, sillor dike. The specimen shown above is abouttwo inches (five centimeters) across.

HORNFELS

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Marble is a non-foliated metamorphic rock

that is produced from the metamorphism oflimestone. It is composed primarily of calciumcarbonate. The specimen shown above is abouttwo inches (five centimeters) across.

MARBLE

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Phyllite is a foliate metamorphic rock that is

made up mainly of very fine-grained mica. Thesurface of phyllite is typically lustrous andsometimes wrinkled. It is intermediate in gradebetween slate and schist. The specimen shownabove is about two inches (five centimetersacross).

PHYLLITE

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Quartzite is a non-foliated metamorphic rock

that is produced by the metamorphism ofsandstone. It is composed primarily of quartz.The specimen above is about two inches (fivecentimeters) across.

QUARTZITE

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Schist is metamorphic rock with welldeveloped foliation. It often contains significantamounts of mica which allow the rock to splitinto thin pieces. It is a rock of intermediatemetamorphic grade between phyllite andgneiss. The specimen shown above is a"chlorite schist" because it contains asignificant amount of chlorite. It is about twoinches (five centimeters) across.

CHLORITE SCHIST

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Schist is metamorphic rock with well

developed foliation. It often contains significantamounts of mica which allow the rock to splitinto thin pieces. It is a rock of intermediatemetamorphic grade between phyllite andgneiss. The specimen shown above is a"garnet schist" because it contains asignificant amount of garnet. The small crystalsvisible in the rock are small red garnets. It isabout two inches (five centimeters) across.

GARNET SCHIST

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Schist is metamorphic rock with well

developed foliation. It often contains significantamounts of mica which allow the rock to splitinto thin pieces. It is a rock of intermediatemetamorphic grade between phyllite andgneiss. The specimen shown above is a"muscovite schist" because it contains asignificant amount of muscovite mica. It isabout two inches (five centimeters) across.

MUSCOVITE SCHIST

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Slate is a foliated metamorphic rock that isformed through the metamorphism of shale. Itis a low grade metamorphic rock that splits intothin pieces. The specimen shown above isabout two inches (five centimeters) across.

SLATE

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Metamorphic rocks have been modified byheat, pressure and chemical process usuallywhile buried deep below Earth's

surface. Exposure to these extreme conditionshas altered the mineralogy, texture andchemical composition of the rocks. There aretwo basic types of metamorphic rocks:1) foliated metamorphic rocks such asgneiss, phyllite, schist and slate which have alayered or banded appearance that is producedby exposure to heat and directed pressure;and, 2) non-foliated metamorphicrocks such as marble and quartzite which donot have a layered or banded appearance.

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