Abrasives A substance (as emery or pumice) used for abrading (to rub or wear away especially by friction) , smoothing, or polishing
Amphibolite facies A rock made up mostly amphibole including minerals like hornblende and plagioclase feldspar.
Anion A negatively charged atom (a building block of matter; combination of protons, neutrons, and electrons ) or group of atoms produced by gain of electrons(fundamental particle of matter, the most elementary unit of negative electrical charge.)
Anthracite A very hard, black coal; has the highest carbon content and heating value; extremely shiny and black, may have a slight golden shine; low density
Aphanitic An igneous rock texture in which individual mineral grains are too small to be distinguished with the naked eye.
Ash Fine particles of volcanic rock and glass blown into the atmosphere by a volcanic eruption.
Augite Dark-green to black glassy mineral of the pyroxene group containing large amounts of aluminum and iron and magnesium


Banded Alternating bands of light and dark-colored minerals
Basaltic A dark, fine-grained, extrusive (volcanic) igneous rock with a low silica content (40% to 50%), but rich in iron, magnesium and calcium. Generally occurs in lava flows, but also as dikes. Basalt makes up most of the ocean floor and is the most abundant volcanic rock in the Earth's crust.
Batholith Very large mass of intrusive (plutonic) igneous rock that forms when magma solidifies at depth. A batholith must have greater than 100 square kilometers (40 square miles) of exposed area.
Bed One of several parallel layers of rock arranged one on top of another; one of a series of layers
Biotite A common rock-forming mineral of the mica family. Biotite is a black or dark brown silicate rich in iron, magnesium, potassium, aluminum, and silica. Like other micas, it forms flat book-like crystals that peel apart into individual sheets on cleavage planes.
Bituminous A harder, more compacted, black coal; Bituminous coal has even more carbon than lignite coal and a correspondingly higher heating value.
Blueschist facies Metamorphic rock rich in bluish colored amphibole.
Bond an attractive force that holds together the atoms, ions, or groups of atoms in a molecule or crystal.
Borate Containing the elements of boron and oxygen
Borate minerals Most borate minerals are found in a type of sedimentary rock that is called an evaporate which is formed by precipitation.
Borax A white crystalline compound that consists of a hydrated sodium borate Na2B4O710H2O, that occurs as a mineral or is prepared from other minerals, and that is used especially as a flux, cleansing agent, and water softener, as a preservative, and as a fireproofing age
Boron A trivalent metalloid element found in nature only in combination and used in metallurgy and in composite structural materials; Pure boron is a little-used dark powder, but boron compounds are important in many industries such as glass and detergent manufacture and agriculture.
Burial metamorphism A form of regional metamorphism that acts on rocks covered by 5 to 10 kilometers of rock or sediment, caused by heat from the Earth's interior and pressure.


Caldera Large, generally circular, fault-bounded depression caused by the withdrawal of magma from below a volcano or volcanoes. Commonly, the magma erupts explosively as from a giant volcano and, falling back to Earth as volcanic ash, fills the caldera so formed.
Carbon A nonmetallic element found native (in the form of diamond and graphite) or as a component of organic compounds
Carbonates The carbonate rocks make up 10 to 15% of sedimentary rocks. They largely consist of two types of rocks. Limestones which are composed mostly of calcite (CaCO3) or high Mg calcite [(Ca,Mg)CO3], and Dolostones which are composed mostly of dolomite [CaMg(CO3)2] Carbonates include the radical "CO3" which reacts with acids to produce carbon dioxide.
Carboniferous period Between 350 and 300 million years ago, (pre-dinosaurs)much of the world was covered with luxuriant vegetation growing in swamps,leaving a deposit with a high percentage of carbon.
Cataclastic Metamorphism caused along a fault. Any rock produced by mainly along fault zones. When stress exceeds breaking strength, a rock yields by rupture. The rock may break as a unit, or individual minerals may be selectively granulated.
Cement A kind of limestone, or a mixture of clay and lime, for making mortar which will harden under water.

Chemical, physical, and biological changes which sediments are converted to rock through deposition or precipitation of minerals in the spaces between grains.

cements: quartz and calcite

Chatoyant Having a changeable luster or color with an undulating narrow band of white light
Chemical families Geologists classify minerals into chemical families based on their compositions. They are divided into classes depending on the anion or positive radical that is part of their chemical formula. These include oxides, sulfides, sulfates, carbonates, silicates, borates, and halides. There are some additional groups.
Chemical sedimentary rocks Sedimentary rock composed of minerals that were precipitated from water. This process begins when water traveling through rock dissolves some of the minerals, carrying them away from their source. Eventually these minerals are redeposited, or precipitated, when the water evaporates away or when the water becomes over-saturated.
Chemical weathering The process that changes the chemical makeup of a rock or mineral at or near the Earth's surface. Chemical weathering alters the internal structure of minerals by the removing and/or adding elements.
Chlorite Family of platy silicate minerals containing various amounts of magnesium, iron, aluminum, water, and small amounts of other elements. Chorites are considered part of the mica family because the crystals form small flakes. Commonly green.
Cinder A bubbly (vesicular) volcanic rock fragment that forms when molten, gas-filled lava is thrown into the air, then solidifies as it falls.
Clastic A sedimentary rock composed of fragments or sediments of pre-existing rock or fossils.
Clastic sedimentary rocks A rock composed of pieces of preexisting rock, cemented together
Cleavage The tendency of a mineral to split along planes determined by the crystal structure; also : the occurrence of such splitting; a fragment (as of a diamond) obtained by splitting
Climatic Of or pertaining to seasonal weather patterns
Color the shade or appearance of a substance; sensation of the eye resulting from stimulation of retina by light waves of certain lengths
Conchoidal fracture A mineral's habit of fracturing to produce curved surfaces like interior of a shell (conch). Typical of glass and quartz.
Concrete Concrete is basically a mixture of two components: aggregates and a cementing agent. The paste, usually comprised of Portland cement and water, binds the aggregates (sand and gravel or crushed stone) into a rocklike mass as the cement hardens because of the chemical reaction of the cement and water.
Contact metamorphism Metamorphism caused by heat from an igneous intrusion including sills, dikes. And other plutons.
Converge A boundary between two plates of the Earth's crust that are pushing together.
Convergent Tending to come together from different directions
Core The innermost layer of the Earth, made up of mostly of iron and nickel. The core is divided into a liquid outer core and a solid inner core. The core is the most dense of the Earth's layers.
Country rock Rocks that were pre-existing. An igneous rocks will squeeze itself through country rocks..
Cross bedding

Cross bedding refers to sedimentary layer deposited at an angle to an underlying set of beds.

Crown The top of a gemstone
Crystal form Geometrical form taken by a mineral, giving external expression to orderly internal atomic arrangement.
Crystalline Having a crystal structure; When referring to sedimentary rocks, crystalline designates a texture in which mineral crystals have formed in an interlocking pattern
Crystallization Growth of minerals (crystalline solids) from a liquid.
Current The portion of a stream or body of water, which is moving with a velocity much greater than the average of the rest of the water.


Debris A type of landslide made up of a mixture of water-saturated rock debris and soil with a consistency similar to wet cement. Debris flows move rapidly downslope under the influence of gravity. Sometimes referred to as earth flows or mud flows.
Decomposition To break up by chemical processes
Deformation General term for folding, faulting, and other processes resulting from shear, compression, and extension of rocks.
Density The quantity per unit volume, unit area, or unit length: as a : the mass of a substance per unit volume b : the distribution of a quantity (as mass, electricity, or energy) per unit usually of space (as length, area, or volume)
Deposit Any accumulation of sediment.
Deposition The natural process of laying down rock layers
Depositional An act or process of depositing
Dike A sheet-like or tabular-shaped igneous intrusion that cuts across the sedimentary layering, metamorphic foliation, or other texture of a pre-existing rock.
Diverge To extend from a common point in different directions; move or draw apart
Divergent A boundary in which two tectonic plates move apart.


Eclogite facies Any member of a small group of igneous and metamorphic rocks whose composition is similar to that of basalt. They are formed when volcanic or metamorphic rocks rich in such mafic minerals are subjected to extremely high pressures and moderate to relatively high temperatures.
Evaporation The process by which any substance is converted from a liquid state into, and carried off in, vapor
Evaporite Rock composed of minerals precipitated from solutions concentrated by evaporation of solvents. Examples: rock salt, gypsum, anhydrite.
Extrusive Igneous rocks that cool and solidify rapidly at or very near the Earth's surface. Also known as volcanic rocks.


Facets The cut face of a gemstone
Feldspar Family of silicate minerals containing varying amounts of potassium, sodium and calcium along with aluminum, silicon and oxygen.. Feldspar crystals are stubby prisms, generally white, gray, or pink.
Fiber optic Fiber optic (or "optical fiber") refers to the medium and the technology associated with the transmission of information as light impulses along a glass or plastic wire or fiber. Fiber optic wire carries much more information than conventional copper wire and is far less subject to electromagnetic interference. Most telephone company long-distance lines are now fiber optic.
Fissures Elongate, narrow fractures.
Flanks The side of a volcano.
Fluid Capable of flowing and easily changing shape
Foliation Aligned layers of minerals characteristic of some metamorphic rocks. Foliation forms in metamorphic rocks when pressure squeezes flat or elongates minerals so that they become aligned. These rocks develop a platy or sheet-like structure that reflects the direction that pressure was applied.
Formation A rock formation is a body of rock of considerable extent with distinctive characteristics that allow geologists to map, describe, and name it.
Fossiliferous sedimentary rocks Sedimentary rocks that contains fossils.
Fracture As mineral characteristic, way in which mineral breaks when it does not have cleavage. May be conchoidal (shell shaped), fibrous, hackly, or uneven.
Fresco The art of painting on freshly spread plaster, before it dries.


Garnet Family of silicate minerals containing varying amounts of aluminum, iron, magnesium, and calcium. Schist and gneiss often have tiny, glassy red garnet crystals.
Gem A precious or sometimes semiprecious stone cut and polished for ornament that has value
Gemologist A person who studies gemstones
Geode Roughly spherical, hollow or partially hollow rock lined with crystals that project toward hollow center. Crystals, often perfectly formed, are usually quartz although calcite and dolomite are also found

A girdle is measured all the way around the outline of the diamond, and must be uniform and fall into thin to slightly thick. Girdle thickness outside of this range can either lead to damage, or add additional weight and cause difficulty in setting.

Glaciers Permanent body of ice, consisting largely of recrystallized snow, that shows evidence of downslope or outward movement due to the stress of its own weight.
Glassy texture Resembling glass in its properties, as in smoothness, brittleness, or transparency
Gneiss A coarse-grained, foliated metamorphic rock that commonly has alternating bands of light and dark-colored minerals.
Granoblastic A texture of roughly equidimensional grains formed by the mutual adjustment of grain boundaries in the solid state.
Granulite facies In rocks of basaltic composition, the granulite results from progressive dehydration of amphibolites at high temperature.
Greenschist facies The name comes from the abundance of the green mineral chlorite in such rocks. These rocks normally show a highly developed foliation and often exhibit strong metamorphic differentiation.


Halides Compound made from a halogen, such as chlorine, iodine, bromine, or fluorine.
Halite A mineral; rock salt or common salt, NaCl. Occurs widely disseminated or in extensive beds and irregular masses precipitated from seawater and interstratified with rocks of other types as true sedimentary rock.
Hardness Mineral's resistance to scratching on a smooth surface. Mohs scale of relative hardness consists of 10 minerals, each scratching all those below it in scale and being scratched by all those above it: 1-talc, 2-gypsum, 3-calcite, 4-flurite, 5-apatite, 6-orthoclase, 7-quartz, 8-topaz, 9-corundum, 10-diamond.
Horizontal beds Thick piles of loose gravel, sand, silt, and mud become layered into flat laying beds.
Hornblende Amphibole family of silicate minerals forming prism or needle like crystals; generally containing iron, magnesium, calcium and aluminum in varying amounts, along with water. Hornblende always has aluminum and is a most common dark green to black variety of amphibole. Actinolite has no aluminum; it and is needle-shaped and light green.
Hornfels A dark, very fine-grained metamorphic rock produced by the recrystallization of a fine-grained rock by heat from a nearby igneous intrusion. From the German, meaning horn rock.
Hornfels facies This facies develops around contact metamorphisms. High temperatures with low pressures.


Igneous Rock formed when molten rock (magma or lava) that has cooled and solidified (crystallized).
Inclusions A gaseous, liquid, or solid foreign body enclosed in a mass (as of a mineral)
Interlocking Joining together tightly.
Intrusive Igneous rock that cools and solidifies beneath the Earth's surface. (= plutonic rock)
Ions Charged atomic particles, produced when an atom gains or loses one or more electrons.


Jeweler One who deals in jewelry , precious stones, watches, and usually silverware and china
Jurassic period A unit of geologic time that began approximately 208 million years ago and ended 144 million years ago. During the Jurassic Period, life included invertebrates, fishes, land plants, amphibians, reptiles, mammals. Near the middle of the Jurassic Period, birds began to appear.


Kimberlite pipes Depending on the magma supply and depth of exposure, these so-called pipes typically range from 50 to 500 meters in diameter. The shape of kimberlite pipes is steeply conical, resembling a carrot shape. They are noted for containing diamonds.
Kyanite An aluminum-rich, blue to light green silicate mineral. Kyanite forms in metamorphic rocks at moderate temperature and high pressure.


Laccolith Is a mushroom-shaped concordant body; large lens shaped body
Lahar A type of mudflow that originates on the slopes of volcanoes when volcanic ash and debris becomes saturated with water and flows rapidly downslope
Lapidarist An expert on precious stones and the art of cutting and engraving them
Lava Magma that reaches the Earth's surface through a volcanic eruption. When cooled and solidified, forms extrusive (volcanic) igneous rock.
Lignite The carbon content is greater in lignite, the lowest rank of coal.
Lithosphere The outer layer of solid rock that includes the crust and uppermost mantle. This layer, up to 100 kilometers (60 miles) thick, forms the Earth's tectonic plates. Tectonic plates float above the more dense, flowing layer of mantle called the asthenosphere.
Luster The manner in which light reflects from the surface of a mineral, described by its quality and intensity.


Magma Molten rock. Magma may be completely liquid or a mixture of liquid rock, dissolved gases and crystals. Molten rock that flows out onto the Earth's surface is called lava.
Magma chambers A body of molten rock and solid crystal mush beneath the Earth's surface. When this chamber cools and solidifies, it is called a pluton.
Magnetism Magnetism is the force where objects are attracted or repelled to one another. Usually these objects are metals containing cobalt, iron, or nickel
Mantle The layer of the Earth below the crust and above the core. The uppermost part of the mantle is rigid and, along with the crust, forms the 'plates' of plate tectonics. The mantle is made up of dense, iron and magnesium rich (ultramafic) rock such as dunite and peridotite.
Marble A metamorphic rock of made of calcium carbonate. Marble forms from limestone by metamorphic recrystallization.
Marine Of or relating to the sea
Matrix Fine-grained material surrounding larger grains in a sedimentary rock.
Mesozoic era An era of geological history comprising the interval between the Permian and the Tertiary or the corresponding system of rocks that was marked by the presence of dinosaurs, marine and flying reptiles, ammonites, ferns, and gymnosperms and the appearance of angiosperms, mammals, and birds
Metallic of, relating to, or being a metal; made of or containing a metal
Metamorphic A rock that has undergone chemical or structural changes produced by increase in heat or pressure, or by replacement of elements by hot, chemically active fluids.
Metamorphism A process whereby rocks undergo physical or chemical changes or both to achieve equilibrium with changing conditions. Agents of metamorphism are heat, pressure, and chemically active fluids.
Metamorphosed The process by which conditions within the Earth, below the zone of diagenesis, alter the mineral content, chemical composition, and structure of solid rock without melting it. Igneous, sedimentary, and metamorphic rocks may all undergo metamorphism
Mica Group of silicate minerals composed of varying amounts of aluminum, potassium, magnesium, iron and water. All micas form flat, plate-like crystals. Crystals cleave into smooth flakes. Biotite is dark, black or brown mica; muscovite is light-colored or clear mica.
Mineral A natural, inorganic crystalline material
Mineralogy A science dealing with minerals , their crystallography, properties, classification, and the ways of distinguishing them
Mohs hardness scale The ten-point scale of mineral hardness , keyed arbitrarily to the minerals 1-talc, 2-gypsum, 3-calcite, 4-flurite, 5-apatite, 6-orthoclase, 7-quartz, 8-topaz, 9-corundum, 10-diamond.
Mollusk Invertebrate having a soft unsegmented body usually enclosed in a shell
Monolith A single stone, especially one of large size, shaped into a pillar, statue, or monument
Mudstone A very fine-grained sedimentary rock formed from mud
Muscovite One of the mica family of minerals. Muscovite is light-colored or clear mica


Native minerals A mineral composed of only one type of element that is naturally occurring
Natural resources Air, water, minerals, fossil fuels, and the plants and animals we use for food and clothing; Natural resources come in two kinds - renewable-resources and non-renewable resources. Non-renewable resources are things that are not replaced by nature, such as fossil fuels.
Nonmetallic Element or compound that does not exhibit metallic luster, conductivity, or other features of metal. Of the elements 17 are non-metals.


Olivine Silicate mineral containing iron and magnesium. A green glassy mineral formed at high temperature. Common in basalt, especially ocean-floor basalt, and in ultramafic rocks. Gem-quality olivine is called peridote. Rock made up entirely of olivine is called dunite.
Olivine Silicate mineral containing iron and magnesium. A green glassy mineral formed at high temperature. Common in basalt, especially ocean-floor basalt, and in ultramafic rocks. Gem-quality olivine is called peridote. Rock made up entirely of olivine is called dunite.
Opalescent Having a play of lustrous rainbow-like colors
Ore The naturally occurring material from which a mineral or minerals of economic value can be extracted at a profit.
Ornamental Serving an esthetic rather than a useful purpose
Oxides Combinations of metal ions with Oxygen, comprises the major ores extracted in mining operations-Hematite (iron ore)-Magnetite (iron ore, magnetic mineral) -Corundum (gemstone, abrasive)


Pavilion Measured from the girdle to the point; bottom portion of a faceted gem
Pegmatites A form of igneous rock consisting of extremely coarse granite resulting from the crystallization of magma rich in rare elements.
Percolates To pass through fine interstices; to filter; as, water percolates through porous stone
Phaneritic An igneous rock texture in which the mineral grains are large enough to be seen with the unaided eye and are of approximately equal size.
Phyllite A foliated metamorphic rock that develops from shate and is marked by a silky sheen and medium grain size.
Physical weathering The disintegration of materials in which no new minerals or substances are formed
Placer deposits A concentration of relatively heavy and resistant minerals in stream or beach deposits; two examples are some deposits of gold and of diamonds.
Pluton A large body of intrusive igneous rock that solidified within the crust. Batholiths and stocks are types of plutons.
Plutonic Rock formed by slow crystallization, which yields coarse texture. Once believed to be typical of crystallization at great depth, but not a necessary condition; any igneous rock that cools beneath the surface. (=intrusive rock).
Polymers A chemical compound or mixture of compounds formed by polymerization (a chemical reaction in which two or more molecules combine to form larger molecules that contain repeating structural units )and consisting essentially of repeating structural units
Pores A minute opening or passageway; an interstice between the constituent particles or molecules of a body; as, the pores of stones.
Porphyritic An igneous rock texture characterized by larger crystals (phenocrysts) in a matrix of distinctly finer crystals (groundmass).
Positive radical An ion with a positive charge
Precipitate A mineral deposited from a water solution in pores or other openings in rocks. Chemical reaction with the surrounding rock, changes in pressure or temperature, or just drying up (evaporation) can cause a mineral to precipitate out of solution. Quartz veins are common products of mineral precipitation; The process that separates solids from a solution.
Precipitation Discharge of water, in rain, snow, hail, sleet, fog, or dew, on land or water surface. Also, process of separating mineral constituents from solution by evaporation (halite, anhydrite) or from magma to form igneous rocks; To precipitate from a solution creating minerals
Pressure One of the main causes of metamorphism
Pyroclastic An igneous rock texture produced from consolidation of fragmented volcanic material ejected during a violent eruption. Also used to describe ash, bombs and other material forcefully ejected during a volcanic eruption


Quartz One of the most common minerals in the Earth's crust. Made up of silicon dioxide (SiO2),lso called silica. Commonly in white masses. Crystals are clear, glassy 6-sided prisms.
Quartzite A nonfoliated metamorphic rock formed from pure, dominantly quartz sandstone. Hard, somewhat glassy-looking rock made up almost entirely of quartz.


Recrystallization Growth of new crystals. No changes in overall chemistry. New crystals grow from the minerals already present.
Refraction Deflection from a straight path undergone by a light ray or energy wave in passing obliquely from one medium (as air) into another (as glass) in which its velocity is different
Regional metamorphism Metamorphism that affects rocks over vast geographic areas stretching for thousands of square kilometers.
Resources All things necessary to human life and civilization that have some value to individuals and/or society
Rock cycle Explains how the three major groups of rock are related to each other. Igneous, sedimentary and metamorphic.
Roundness Angularity/roundness refers to whether the grains are smooth or jagged


Sand A type of clastic sediment that is small, but larger than mud particles and smaller than pebbles
Sand dunes Landform made from wind blowing on sand that makes ridges. Stronger winds make bigger dunes and lighter winds make smaller dunes
Schist Metamorphic rock usually derived from fine-grained sedimentary rock such as shale. Individual minerals in schist have grown during metamorphism so that they are easily visible to the naked eye. Schists are named for their mineral constituents. For example, mica schist is conspicuously rich in mica such as biotite or muscovite.
Sedimentary Sedimentary rocks are formed from pre-existing rocks or pieces of once-living organisms. They form from deposits that accumulate on the Earth's surface. Sedimentary rocks often have distinctive layering or bedding.
Sedimentary environment A sedimentary environment is an area of the Earth's surface where sediment is deposited. It can be distinguished from other areas on the basis of its physical, chemical, and biological characteristics.
Sedimentary rock Sedimentary rocks are formed from pre-existing rocks, pieces of once-living organisms, or chemical means.. Sedimentary rocks often have distinctive layering or bedding.
Sedimentary structures Are those which form during (or shortly after) deposition of the sediment. Some sedimentary structures are created by the water or wind which moves the sediment. Other sedimentary structures form after deposition - such as footprints, worm trails, or mudcracks.
Sedimentation The act of depositing sediments; the deposition of the material of which sedimentary rocks are formed.
Sedimentologists The study of sedimentology or the study of sedimentary rocks.
Seduction Process of one crustal plate sliding down and below another crustal plate as the two converge. The subduction zone is the area between the two plates, somewhat like a giant reverse fault.
Semimetals an element (as arsenic) possessing metallic properties in an inferior degree and not malleable
Serpentinite A family of silicate minerals rich in magnesium and water, derived from low-temperature alteration or metamorphism of the minerals in ultramafic rocks. Rocks made up of serpentine minerals are called serpentinite. Serpentine minerals are light to dark green, commonly varied in hue, and greasy looking; the mineral feels slippery.
Shale Sedimentary rock derived from mud. Commonly finely laminated (bedded). Particles in shale are commonly clay minerals mixed with tiny grains of quartz eroded from pre-existing rocks.
Shearing Stress that slices rocks into parallel blocks that slide in opposite directions along their adjacent sides. Shearing stress may be caused by transform motion.
Silicates A salt or ester derived from a silicic acid; especially : any of numerous insoluble often complex metal salts that contain silicon and oxygen in the anion, constitute the largest class of minerals, and are used in building materials (as cement, bricks, and glass)
Sill A sheet-like or tabular-shaped igneous intrusion that cuts across the sedimentary layering, metamorphic foliation, or other texture of a pre-existing rock.
Sillimanite Brown, pale green, or white glassy silicate mineral that often occurs in long, slender, needlelike crystals frequently found in fibrous aggregates.
Siltstone A sedimentary rock made mostly of silt-sized grains. (Silt -loose particles of rock or mineral (sediment) that range in size from 0.002 - 0.0625 millimeters in diameter. Silt is finer than sand, but coarser than clay.)
Slate A fine-grained, foliated metamorphic rock that develops from shale and tends to break into thin, flat sheets.
Sorting The range of grain sizes in a sedimentary rock.
Specific gravity The ratio of the density of a material to the density of water.
Stalactites A calcite mineral deposit which hangs downwards from a roof or wall of a cave.
Stalagmites A cylinder of calcium carbonate projecting upward from the floor of a limestone cave
Staurolite A silicate mineral that is common in metamorphic rocks. Short prismatic crystals, some cross shaped, reddish to dark brown
Stones A general term for all rocks and minerals.
Streak The color of a mineral in its powdered form, usually obtained by rubbing the mineral against an unglazed porcelain tile to see the mark it makes. A mineral harder than the tile must be pulverized by crushing.
Stress The force acting on a rock or another solid to deform it,
Subducting Process of one crustal plate sliding down and below another crustal plate as the two converge.
Sulfates Metal ions combine with the Sulfate ion (SO4), atomic structure sometimes can allow bonding of water molecules - Gypsum (plaster)-Barite (drilling mud)
Sulfides Mineral formed by direct union of element with sulfur. Examples: argentite, chalcocite, galena, sphalerite, pyrite, and cinnabar.
Symmetry The property of being symmetrical; especially : correspondence in size, shape, and relative position of parts on opposite sides of a dividing line or median plane or about a center or axis


Taste To ascertain the flavor of by taking a little into the mouth
Temperature The degree of hotness or coldness of the atmosphere with respect to some standard value.
Tephra General term for all sizes of particles ejected into the air during volcanic eruptions. Includes particles as tiny as volcanic ash and as large as bombs and blocks
Texture A description of the variation of the intensity of a surface, quantifying properties such as smoothness, coarseness and regularity.
Thunderegg Thundereggs range in diameter from less than one inch to over four feet. Nondescript on the outside, they reveal exquisite designs in a wide range of colors when cut and polished; round rocks with agate in them; Indians once thought they were eggs laid by the Thunderbird.
Tuffs Volcanic rock made up of rock and mineral fragments in a volcanic ash matrix. Tuffs commonly are composed of much shattered volcanic rock glass--chilled magma blown into the air and then deposited. If volcanic particles fall to the ground at a very high temperature, they may fuse together, forming a welded tuff.
Tumbling A method to round gemstones by polishing


Ulexite (NaCaB5O6(OH)6_5H2O A mineral consisting of a hydrous borate of sodium and calcium and usually occurring in loosely packed white fibers that transmit light lengthwise with nearly undiminished intensity


Vent The opening at the Earth's surface through which volcanic materials issue forth.
Vesicular Vesicles are holes, usually spherical, to tubular, to oval in shape
Volcanic Igneous rock that cools and solidifies at or very near the Earth's surface. Volcanoes produce volcanic rock


Weathered Weathering includes two surface or near-surface processes that work in concert to decompose rocks. Chemical weathering involves a chemical change in at least some of the minerals within a rock. Mechanical weathering involves physically breaking rocks into fragments without changing the chemical make-up of the minerals within it.
Weathering The destruction of rocks at the Earth's surface; The chemical alteration and mechanical breakdown of rock materials during exposure to air, moisture, and organic matter.




Zeolite facies The rocks of which formed at the lowest temperatures and pressures associated with regional metamorphism. It represents the transition between the sedimentary processes of diagenesis and the distinct regional metamorphism exhibited by the greenschist facies.