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Erth2404 - Engineering Geoscience Lab
Practical Study Guide.
Phaneritic - answer✔coarse-grained, crystals are large enough to be seen w/out a microscope,
formed by slow cooling (intrusive)
Pegmatitic - answer✔Very large crystals formed by extremely slow cooling. Rich in volatiles.
Aphanitic - answer✔Rapid cooling at earth's surface results in tiny mineral crystals that can only
be seen under a microscope. Micro-crystals.
Porphyritic - answer✔Type of texture where there are two distinct sizes of crystals in the rock.
Vesicular - answer✔A texture found in extrusive igneous rocks where there are many spherical
or ovoid holes or vesicles present in the rock.
Glassy - answer✔crystal unable to form; Rapid rate of cooling prevents crystals from forming
(e.g. Obsidian)
Pyroclastic - answer✔A special category of volcanic rocks. Formed from the expulsion of ash,
cinders, bombs, and gases during an explosive volcanic eruption.
Mafic - answer✔Igneous Rock containing large amounts of Iron and Magnesium, dark in color
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Felsic - answer✔Describes magma or igneous rock that is rich in feldspars and silica and that is
generally light in color.
Sedimentary rock - answer✔A type of rock that forms when particles from other rocks or the
remains of plants and animals are pressed and cemented together
Igneous rock - answer✔A type of rock that forms from the cooling of molten rock at or below
the surface
Metamorphic - answer✔A type of rock that forms from an existing rock that is changed by heat,
pressure, or chemical reactions.
Organic Sedimentary Rock - answer✔Sedimentary rock (such as coal) formed from carbon-rich
relicts of organisms.
Chert/Flint - answer✔An impure sedimentary rock, often gray, that consists primarily of
extremely small quartz (Silica) crystals precipitated from watery solutions.
Carbonate - answer✔Is a common mineral that occurs as the major constituent of limestone or
as the cementing material in clastic rocks. (Calcite CaCO3) a weak reaction will occur if you
scratch the rock and apply HCl.
Clastic - answer✔A sedimentary rock composed of weathered fragments of older rock.
Evaporites - answer✔sedimentary rocks formed from minerals left after water evaporates
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Lithic Fragments - answer✔Sedimentary rocks that contain fragments of rocks and/or minerals
as coarse clastic material (gravel or sand-sized particles e.g. Conglomerates)
Feldspar - answer✔In some circumstances, sedimentary rocks may often contain significant
amounts of feldspar. Feldspar often break down into clay minerals during weathering. (e.g.
plagioclase and orthoclase)
Aluminous - answer✔Protolith is shale or mudrock, contains abundant aluminum.
Quartzo-feldspathic - answer✔If the protolith is a felsic igneous rock that contains abundant
feldspar and quartz.
Calcerous - answer✔If the protolith is a carbonate sedimentary rock (e.g. calcite, dolostone)
Slaty - answer✔Describing a rock that splits easily along nearly flat and parallel planes.
Phyllitic - answer✔refers to the alignment of platy (sheet-like) minerals into a layered structure,
where the minerals are too small to recognize. Biggest distinction between phyllite and schist is
usually crystal size.
Schistose - answer✔The texture of a rock in which visible platy or needle-shaped minerals have
grown essentially parallel to each other under the influence of directed pressure. Have a shiny
metallic appearance.
Gniessic - answer✔Coarsely foliated texture in which the minerals have been segregated into
compositional layers or bands.
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ALL RIGHTS RESERVED.
Erth2404 - Engineering Geoscience Lab
Practical Study Guide.
Phaneritic - answer✔coarse-grained, crystals are large enough to be seen w/out a microscope,
formed by slow cooling (intrusive)
Pegmatitic - answer✔Very large crystals formed by extremely slow cooling. Rich in volatiles.
Aphanitic - answer✔Rapid cooling at earth's surface results in tiny mineral crystals that can only
be seen under a microscope. Micro-crystals.
Porphyritic - answer✔Type of texture where there are two distinct sizes of crystals in the rock.
Vesicular - answer✔A texture found in extrusive igneous rocks where there are many spherical
or ovoid holes or vesicles present in the rock.
Glassy - answer✔crystal unable to form; Rapid rate of cooling prevents crystals from forming
(e.g. Obsidian)
Pyroclastic - answer✔A special category of volcanic rocks. Formed from the expulsion of ash,
cinders, bombs, and gases during an explosive volcanic eruption.
Mafic - answer✔Igneous Rock containing large amounts of Iron and Magnesium, dark in color
1|Page
, ©BRAINBARTER EXAM SOLUTIONS 2024/2025
ALL RIGHTS RESERVED.
Felsic - answer✔Describes magma or igneous rock that is rich in feldspars and silica and that is
generally light in color.
Sedimentary rock - answer✔A type of rock that forms when particles from other rocks or the
remains of plants and animals are pressed and cemented together
Igneous rock - answer✔A type of rock that forms from the cooling of molten rock at or below
the surface
Metamorphic - answer✔A type of rock that forms from an existing rock that is changed by heat,
pressure, or chemical reactions.
Organic Sedimentary Rock - answer✔Sedimentary rock (such as coal) formed from carbon-rich
relicts of organisms.
Chert/Flint - answer✔An impure sedimentary rock, often gray, that consists primarily of
extremely small quartz (Silica) crystals precipitated from watery solutions.
Carbonate - answer✔Is a common mineral that occurs as the major constituent of limestone or
as the cementing material in clastic rocks. (Calcite CaCO3) a weak reaction will occur if you
scratch the rock and apply HCl.
Clastic - answer✔A sedimentary rock composed of weathered fragments of older rock.
Evaporites - answer✔sedimentary rocks formed from minerals left after water evaporates
2|Page
, ©BRAINBARTER EXAM SOLUTIONS 2024/2025
ALL RIGHTS RESERVED.
Lithic Fragments - answer✔Sedimentary rocks that contain fragments of rocks and/or minerals
as coarse clastic material (gravel or sand-sized particles e.g. Conglomerates)
Feldspar - answer✔In some circumstances, sedimentary rocks may often contain significant
amounts of feldspar. Feldspar often break down into clay minerals during weathering. (e.g.
plagioclase and orthoclase)
Aluminous - answer✔Protolith is shale or mudrock, contains abundant aluminum.
Quartzo-feldspathic - answer✔If the protolith is a felsic igneous rock that contains abundant
feldspar and quartz.
Calcerous - answer✔If the protolith is a carbonate sedimentary rock (e.g. calcite, dolostone)
Slaty - answer✔Describing a rock that splits easily along nearly flat and parallel planes.
Phyllitic - answer✔refers to the alignment of platy (sheet-like) minerals into a layered structure,
where the minerals are too small to recognize. Biggest distinction between phyllite and schist is
usually crystal size.
Schistose - answer✔The texture of a rock in which visible platy or needle-shaped minerals have
grown essentially parallel to each other under the influence of directed pressure. Have a shiny
metallic appearance.
Gniessic - answer✔Coarsely foliated texture in which the minerals have been segregated into
compositional layers or bands.
3|Page
