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Rock - naturally occurring solid aggregate of one or more minerals.
Petrology is the scientific study of rocks.
Petrologists classify rocks based on how they were formed.
Types of Rock�
Rock Classification
Rock Classification
Igneous rocks are formed by the cooling or solidification of magma or lava.
Igneous rock
Differentiate magma and lava.
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Two types of igneous rock:
A. Extrusive/Volcanic rock - forms when magma makes its way to Earth’s surface as lava and then cools. The crystals are very small (fine-grained) since the cooling process is fast.
B. Intrusive/Plutonic - It cools slowly beneath the Earth surface and are created by magma. The intrusive igneous rocks have very large crystals (coarse grained).
Two Types of Igneous Rock:
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Igneous rocks are classified based on:
1. Composition- it refers to rock’s mineral and chemical make-up.
Felsic – igneous rocks that are light in colors; feldspar and silicates
Mafic – dark-colored igneous rocks made up of magnesium, calcium and iron
Intermediate – refers to igneous rocks between mafic and felsic composition.
Ultramafic – denotes igneous rocks that composed chiefly of mafic minerals.
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Igneous rocks are classified based on:
2. Texture - overall appearance of a rock based on the size, shape, and arrangement
of interlocking mineral crystals.
Aphanistic – fine-grained rocks with crystals seen by aid of microscope.
Phaneritic - coarse-grained rocks
Porphyritic – large crystals with small crystals
Glassy - a rock that looks like colored glass with no visible mineral crystal.
Pyroclastic- results from explosive fragmentation of volcanic material.
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Rock Classification
Sedimentary rocks are formed by the accumulation compaction and cementation of sediments, a process called lithification.
Sedimentary processes
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Three types of sedimentary rocks
a. Clastic Sedimentary rock - formed from accumulation of clasts: little pieces of broken rocks and shells. Examples: conglomerate, breccia, sandstone, shale
b. Chemical - formed when dissolved minerals precipitate from a solution.
Example: Halite - formed when a body of seawater becomes closed off and evaporates.
c. Organic - rocks formed from the accumulation of animal debris
Example: Coal - composed of organic matter in the form of plants fragment
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Rock Classification
Metamorphic rocks are formed by preexisting rocks that are exposed to extreme heat and pressure in the Earth’s interior, a process called
metamorphism.
Two Types of Metamorphism��
2. Contact-the rock minerals and textures are changed mainly by heat due to contact with magma.
Igneous rocks are based on:��
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Felsic – igneous rocks that are light in colors; feldspar and silicates Mafic – dark-colored igneous rocks made up of magnesium, calcium and iron
Intermediate – refers to igneous rocks between mafic and felsic composition. Ultramafic – denotes igneous rocks that composed chiefly of mafic minerals.
Igneous rocks are based on:��
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2.Texture - refers to the size arrangement and grains within the rock.
Foliation - any planar arrangement of mineral grains or structural features within the rock.
a. Foliated rocks – can be arranged in terms of increasing metamorphism,
and it appeared layered or banded with compressed mineral grains.
Example: mica
b. Non-foliated rocks – usually made up of only few minerals.
Key Points:
Rock Classification
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What I Have Learned; page 11 Activity 6 Compare Me!
Fill in the Venn Diagram to determine the similarities and
differences of the three types of rocks.