versus

Rock on!

Igneous Rocks

…are solidified from mineral matter in a high-temperature

molten state.

Sedimentary Rocks

…are layered accumulations of mineral particles derived mostly by weathering

and erosion of preexisting rocks.

Metamorphic Rocks

…are formed from rocks that have been physically or chemically changed, usually by

application of heat and pressure during crustal mountain-making.

Difference between Minerals and Rocks

• A mineral is a solid, inorganic, naturally-forming material of the Earth that has both a known chemical composition and a crystalline structure with distinct physical properties that is unique to that mineral

• A rock is a solid aggregate of one or more minerals that have been cohesively brought together by a rock-forming process.

Igneous Rocks- ‘Fire’ rocks - Formed either underground or

above ground. - Underground, they are formed

when magma becomes trapped in small pockets and cool slowly (intrusive)

- Above ground, igneous rocks form when volcanoes erupt, causing magma to come to the surface (called lava) and cools (extrusive)

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Igneous Rock Observable Characteristics

Location of Formation

Example

Volcanic (Extrusive) Crystals so small you can't see them with the unaided eye. Sometimes there are larger, visible crystals in a very fine-grained matrix.

These rocks were once liquid magma that erupted from volcanoes. They cooled very quickly, which is why the crystals are usually very small.

Basalt – usually dark gray to black, fine-grained volcanic rock; sometimes has gas bubbles (vesicles)

Intrusive Interlocking Crystals These rocks were once liquid magma, but they did not erupt from volcanoes. Instead, they cooled slowly underground. The crystals had time to grow large. We see them because erosion has stripped off and removed all of the rock above it.

Granite – pinkish, whitish igneous rock with interlocking crystals of quartz and feldspar. Sometimes includes mica.

Igneous Rock ClassificationCommon Igneous Rocks

Classification Igneous Rock

Color Common Minerals

Intrusive Igneous Rocks

Granite Felsic(light-colored)

Quartz, potassium feldspar, plagioclase feldspar, mica

Diorite Intermediate Plagioclase feldspar, amphibole, pyroxene, mica

Gabbro Mafic(dark-colored)

Plagioclase feldspar, pyroxine, olivine

Extrusive Igneous Rocks

Rhyolite Felsic Quartz, potassium feldspar, plagioclase feldspar, mica

Andesite Intermediate Plagioclase feldspar, amphibole, pyroxene, mica

Basalt Mafic Plagioclase feldspar, pyroxine, olivine

Pumice Felsic/Intermediate

Various silicates

Obsidian Variable Various silicates

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Sedimentary Rocks- ‘Water’ rock- Over millions of years, rocks

are eroded and weathered and transported by wind and water to eventually settle in the bottom of rivers, lakes or oceans.

- Layer after layer of eroded earth are deposited on top of each other.

- These layers are compressed over time, until the bottom layers slowly turn into rock under great pressure.

- These layered rocks that form are called sedimentary rocks

Sedimentary Observable Characteristics

Location of Formation

Example

Clastic Made up of smaller rocks cemented together. Sometimes has fossils. Usually has layers.

These rocks formed when loose sediment (rocks, sand) were deposited by water, compacted, and cemented together. These rocks form along beaches, by rivers, or under the water in lake or oceans.

Conglomerate – composed of pieces pebble-size or larger

Sandstone - composed of sand-size pieces

Shale - composed of pieces smaller than fine sand

Chemical Usually a light gray, sometimes with crystals, sometimes with shells, sometimes just massive.

These rocks are also deposited in water. However, they form as a chemical reaction in the water that leaves a chemical deposit, usually on an ocean bottom.

Limestone – a whitish or grayish rock made of the mineral calcite.

Sedimentary Rock ClassificationCommon Sedimentary Rocks

Classification

Sedimentary Rock

Composition Depositional Environment

Clastic (Detrital)

Shale Clay and/or silt Swamp, floodplain, river bottom

Sandstone Sand Beach, desert

Conglomerate

Various-sized pebbles

Riverbed

Non-Clastic(Chemical)

Limestone Calcite or fragmented shells

Shallow sea, coastline

Chert (flint) Chalcedony (quartz), traces of other minerals

Formed from a silica-rich precipiate in a deep ocean environment.

Bituminous Coal

Plant material Ancient forest or swamp

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Metamorphic Rocks - Rocks that have "morphed"

into another kind of rock - Morphing happens under

tons of pressure, which fosters heat build up, and this causes them to change.

- This explains why some metamorphic rock samples have flattened grains.

Metamorphic Observable Characteristics

Location of Formation

Example

Usually has interlocking crystals and layers (called foliation)

These rocks formed when igneous, sedimentary, or other metamorphic rocks are heated and/or squished, forming a new rock type. This usually happens during mountain building events (regional metamorphism), but also happens during igneous activity (contact metamorphism).

Quartzite – metamorphosed sandstone

Slate – metamorphosed shale.

Schist – metamorphosed sedimentary rocks that had lots of clay.

Gneiss – metamorphosed granite.

Metamorphic Rock Classification

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Common Metamorphic Rocks

Classification

Metamorphic Rock

Parent Rock Common Minerals

Foliated (Banded)

Slate Shale, mudstone Quartz, clay minerals (feldspars)

Schist Shale, slate, basalt, or granite Mica, chlorite, talc, quartz

Gneiss Shale, schist, granite, sandstone, and other rock types

Quartz, feldspars

Non-Foliated(Not Banded)

Quartzite Sandstone Quartz

Marble Limestone, dolomite Calcite

Anthracite coal

Bituminous coal Crystalline carbon