click below
click below
Normal Size Small Size show me how
Topic 9
Rocks and Minerals
Term | Definition |
---|---|
Banding | A form of foliation that consists of alternating light (quartz) and dark (biotite or hornblende) minerals found in metamorphic rocks. |
Basalt | An extrusive igneous rock having a fine-grained texture and mafic composition (plagioclase feldspar, pyroxene, olivine, and amphibole). |
Bituminous coal | Soft coal. The most abundant form of coal. Coal that contains a large amount of volatile matter. Coal formed by sedimentary processes. |
Breccia | An inorganic land-derived sedimentary rock composed of angular, pebble-sized particles; a rock similar to conglomerate, but with angular pebbles rather than the smooth pebbles contained in conglomerates. |
Cementation | The process by which sediments are converted into sedimentary rock. Three common cements are silicon dioxide (silica), calcium carbonate (calcite), and iron oxide (hematite). |
Clastic sedimentary rocks | Rocks that form when sediments are deposited, compressed, dewatered and cemented together. Examples include: conglomerate, breccia, sandstone, siltstone, and shale. |
Clastic sedimentary texture | A texture classification of sedimentary rocks that includes rocks composed of fragments of earth materials that are cemented together; inorganic land-derived sedimentary rocks. |
Clay | A soil particle or sediment having a diameter less than 1/256 mm. Generally, the smallest particles that will settle out of a suspension. Clay also refers to a group of minerals that include kaolin, montmorillonite, and illite. |
Cleavage | The property of a mineral that breaks along flat surfaces or planes. |
Coarse texture | Composed of large particles, fragments or crystals. |
Color | The wavelength of light reflected by an object. |
Compaction | The reduction of the thickness of sediments as a result of the weight and pressure caused by overlying material. |
Conglomerate | A clastic sedimentary rock composed primarily of rounded pebble-sized particles that are held together by a natural cement. |
Contact metamorphism | A form of thermal metamorphism that occurs as a result of igneous intrusion. Heat and hydrothermal solutions from the igneous material causes the alteration of the pre-existing rocks. |
Density | The property of matter that indicates the mass per unit volume. Density provides an indication of the packing of the particles of matter. Density is calculated by the equation: |
Diameter | The distance across a circle that passes through the center of the circle. |
Erosion | The breakdown and removal of earth material by specific agents, such as gravity, ground water, running water, ice, wind, wave action, turbidity currents, and human activities. |
Evaporite | Any sedimentary rock that forms from the evaporation of water. |
Extreme pressure | The force produced by the weight of overlying rocks or movement of large regions of the Earth’s crust. Pressure acting on rocks located below the surface. |
Extrusive igneous rock | Rock formed from the solidification of molten material at or near the surface. |
Folding | The plastic deformation of rocks that results in the formation of monoclines, anticlines, and synclines. |
Foliated | A texture found in metamorphic rocks in which the flat minerals, such as mica, form along planes. |
Fossil | Any remains, trace, imprints, or other evidence of pre-existing life that is preserved in the rock record. |
Fracture | The way a mineral breaks, other than along smooth planes. Types of fracture include: conchoidal, smooth, splintery, and hackly. |
Gabbro | An intrusive igneous rock having a coarse-grained texture and a mafic composition (plagioclase feldspar, pyroxene, amphibole, and olivine). |
Glacial activity | Any process that is related to movement of large masses of ice. Erosion and/or deposition by glaciers. |
Gneiss | A high-grade metamorphic rock that generally is foliated and banded. A metamorphic rock having a gneissic texture. |
Granite | An intrusive igneous rock having a coarse-grained texture and a felsic composition (potassium feldspar, quartz, muscovite mica, biotite mica, and hornblende). |
Gypsum | An evaporite mineral composed of calcium sulfate and water of crystallization. Mineral with a hardness of 2 on Moh’s Scale of Hardness. Alabaster. |
Halite | Rock salt. Sodium Chloride (NaCl). The primary sodium salt that forms when sea water evaporates. A mineral with cubic cleavage. |
Hardness | The ability of a mineral to resist being scratched. Moh’s Scale of Hardness compares the hardness of minerals to each other |
Heat | The quantity of thermal energy in a mass or an object. |
Hornblende | The most common amphibole mineral; a ferromagnesian mineral in which the silicon-oxygen tetrahedra form double chains (inosilicate structure). |
Igneous rock | Any rock formed from the cooling and solidification of molten material (magma or lava). Examples of igneous rocks include: rhyolite, granite, basalt, gabbro and peridotite. |
Intrusive igneous rock | Rock formed from the solidification of magma deep below the surface. |
Limestone | Any sedimentary rock that is composed primarily of calcium carbonate (lime). Limestones can form by deposition of lime muds, precipitation of crystals, or by the secretions of living organisms. |
Luster | The appearance of a mineral in reflected light; the way that a mineral reflects light. Luster is subdivided into metallic and nonmetallic. |
Mafic | Any igneous rock containing an abundance of ferromagnesian minerals. The mineral composition gives the resulting rock a dark color and high density. |
Magma | Molten rock found beneath the Earth’s surface. A silicate melt that can intrude into existing rock or extrude onto the surface, forming lava. |
Magnetism | The force produced by a magnet or magnetic field. |
Marble | A monominerallic metamorphic rock composed of the mineral calcite. Dolomitic marble is composed of the mineral dolostone Marbles from from the metamorphosis of limestone (protolith).. |
Metaconglomerate | A metamorphic rock derived from conglomerate (protolith). A coarse-textured, massive, metamorphic rock composed almost exclusively of quartz. |
Metamorphic rock | Any rock that forms as a result of changes that occur in pre-existing rock material. Metamorphic rocks form as a result of heat (thermal metamorphism) and/or pressure (dynamic metamorphism). Examples of metamorphic rocks include: slate, schist, gneiss, |
Metamorphism | The processes resulting from heat and pressure that change one form of rock to another form of rock. |
Mica | Muscovite and Biotite. A group of silicate minerals in which the atoms are arranged in sheets or layers. A major group of rockforming minerals. |
Mineral | Any naturally occurring, inorganic solid, with a definite chemical composition. Minerals are generally identified on the basis of their physical properties. |
Monomineralic rock | Any rock composed primarily of one mineral. For example, limestone and marble are composed of the mineral calcite. |
Mountain | A landscape region with high relief (measured in thousands of meters) and complex rock structure. There are four basic types of mountains: fault block, folded, domed or upwarped, and volcanoes. |
Non-foliated | Massive metamorphic rocks in which the comprising minerals are randomly oriented. |
Olivine | A ferromagnesian, silicate mineral with a structure containing individual or isolated tetrahedrons. A mineral common in rocks with an ultra mafic composition, such as peridotite and dunite. |
Pebble | A rock fragment, soil particle, or sediment having a diameter in the range of 0.2 cm to 6.4 cm. A rounded fragment that is larger than a sand grain and smaller than a cobble. |
Pegmatite | A plutonic igneous rock that is composed of very large crystals. Igneous rocks that form deep under ground cool and crystallize very slowly and therefore contain crystals that are very large. |
Phyllite | A foliated metamorphic rock containing mica, quartz, feldspar, amphibole, and garnet; formed by regional metamorphism of slate; the foliated surfaces have a shiny appearance from microscopic crystals of mica; a type of metamorphic rock between slate/shist |
Plagioclase feldspar | A group of feldspar minerals that contain sodium (albite) and calcium (anorthite) and are found in minerals with mafic compositions. |
Plutonic rocks | Intrusive igneous rocks; igneous rocks that form as a result of the solidification of magma at great depths. Plutonic rocks have coarse textures because of the slow rates of cooling and crystallization. |
Polymineralic rock | Any rock composed of two or more minerals. For example, granite may be composed of the minerals: orthoclase feldspar, quartz, muscovite mica, and amphibole. |
Pressure | Force per unit area. Ast he depth within the Earth increases the pressure on the earth materials increases. |
Pyroxene | A group of ferromagnesian, silicate minerals with a single chain structure. The group of rock-forming minerals that contains the mineral augite. |
Regional metamorphism | Changes in rocks that occur over large areas as a result of heat and pressure associated with tectonic activity and/or mountain building |
Rhyolite | An extrusive igneous rock having a fine-grained texture and a felsic composition (orthoclase feldspar, quartz, muscovite mica biotite mica, and amphibole)., |
Rock cycle | A model that represents the sequences that are involved in formation, alteration, and the changes of the various types of rocks. |
Rock gypsum | sedimentary rock composed primarily of the mineral gypsum (CaSO4) |
Rock salt | A sedimentary rock composed primarily of the mineral halite (salt). |
Sand | A rock fragment, soil particle, or sediment having a diameter in the range of 1/16mm to 2mm. Sediment or soil particle that is larger than silt and smaller than a pebble. |
Sandstone | A clastic sedimentary rock composed primarily of sand grains that are held together by a natural cement. |
Sedimentary rock | A layered rock formed by the compaction and cementation of sediments; chemical precipitation; or organic origins. Examples of sedimentary rocks include: conglomerate, sandstone, shale, and limestone. |
Sediments | Any solid material that is transported and deposited by an agent of erosion, chemically precipitated from water, or secreted by an organism. Layers of unconsolidated sediments may be compacted, dewatered, and cemented together |
Shale | A fine-grained, clastic sedimentary rock composed primarily of clay. |
Silt | A soil particle or sediment having a diameter in the range of 1/256mm to 1/16mm. An accumulation of particles that are larger than clay and smaller than sand. |
Siltstone | A clastic sedimentary rock formed primarily by silt-sized particles that are held together by a natural cement. |
Streak | The color of the powder or fresh surface of a mineral. |
Texture | The size, shape and arrangement of the crystals or particles of soil, rocks, or minerals. |
Weathering | The mechanical or chemical breakdown of rock material as a result of interactions with atmospheric conditions. |
Wind | The horizontal movement of air. Surface winds are the result of the differential heating of the Earth. Advection. |