Rocks Rock!!!!
What Are Rocks?
-rocks are any solid mass of mineral or mineral-like matter occurring naturally as part of our planet. -there are Three Types of Rocks classified by how they were formed. What Is Igneous Rock? -it is formed by the crystallization of molten magma. How Does Igneous Rock Form? -intrusive igneous rocks are formed when magma hardens beneath Earths surface. (larger crystals due to slow cooling) -extrusive igneous rocks are formed when lava hardens. How Do We Classify Igneous Rock? -igneous rocks can be classified based on their composition and texture. 1.Texture -Coarse-grained texture is caused by slow cooling resulting in larger crystals -fine-grained texture is cause by rapid cooling resulting in smaller interconnected mineral grains. 1. Texture (cont.) -glassy texture is caused by very rapid cooling. -porphyritic texture is cause by different rates of cooling resulting in varied sized minerals. 2. Composition -granite composition rocks are made mostly of light-colored quartz and feldspar. -basaltic composition rocks are made mostly of dark-colored silicate minerals and plagioclase -andesitic composition rocks are between granitic light-color minerals and basaltic composition dark-colored minerals. |
Sedimentary rock
-formed from the weathered products of preexisting rocks that have been transported, deposited, compacted, and cemented. How does Sedimentary Rock Form? -weathering involves rock being broken apart by weather- freezing/thawing water or wind -erosion involves the weathering and the removal of rock. -deposition occurs when an agent of erosion-water, wind, ice, or gravity-loses energy and drops sediments. -Compaction is a process that squeezes, or compacts, sediments. -Cementation takes place when dissolved minerals are deposited in the tiny spaces among the sediments. how do we classify sedimentary rocks? 1.Clastic sedimentary rocks are composed of weathered bits of rocks and minerals. -classified by particle size -common rock -shale, sandstons, conglomerate 2. chemical sedimentary rocks form when dissolved substances precipitate, or separate from water. -common rocks -limestone-most abundant chemical rock -microcrystalline quartz known as chert, flint, jasper, or agate -evaporites such as rock salt or gypsum -coal What are Metamorphic Rocks? -metamorphism means "to change form". -it occurs at elevated temperatures and pressures. -conditions for formation are found a few kilometers below the Earths surface and extend into the upper mantle. How Is Metamorphic Rocks Made? -Contact metamorphism occurs when magma moves into rock. -occurs near a body of magma -changes are driven by a rise in temperature -Regional metamorphism results from large-scale deformation (folding) and high-grade metamorphism -direct pressures and high temperatures occur during mountain building. -produces greatest volume of metamorphic rock. -Hydrothermal solutions -hot water-based solutions escaping from the mass of magma -promote recrystallization by dissolving original minerals and then depositing new ones. How do We Classify Meta Rocks -1.foliated metamorphic rock-banded or layered appearance -2.Nonfoliated-does not have a banded texture |
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Mineral Properties
What Are The Properties Of Minerals
-color- although an obvious feature, it is often unreliable to use to determine the type of mineral. -streak- the color of a mineral in its powdered form; obtained by rubbing the mineral against an unglazed porcelain plate. (-streak is usually less variable than color, and useful for distinguishing between minerals with metallic luster). -luster- this property describes the appearance of reflected light from the minerals surface. Nonmetallic minerals are described using the following term: vitreous, pearly, silky, resinous, and earthy. -hardness- how easy you can scratch the surface of a mineral. Mohs hardness scale, tale is the softest, hardest is diamond. -cleavage- orientation and number of planes of weakness within a mineral. directly reflects the orientation of weak bonds within the crystal structure. This feature is also highly diagnostic. -fracture- this describes how a mineral breaks if it is not along well defined planes. in minerals with low symmetry and highly interconnected atomic networks, irregular fracture is common. -density/specific gravity- defined as the mass divided by the volume and normally designated by the Greek letter, rho. |
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