Glossary of Geological Words and Terms Associated with Geological Information, Specimen Content and Origin

transparent minerals with a very high luster and ability to reflect and transmit light
Adularia: a feldspar of (potassium aluminum silicate) found in moonstone
Adularescence: a shimmering play of light reflecting from within a stone, such as in moonstone
Aggregate: a composite of rocks and minerals such as stream beds that include sand and boulders which over time can form layers or larger boulders that have been naturally cemented together
Almandine: an iron aluminum silicate mineral of the garnet group which is deep red to reddish purple
Aluminum: a member of the periodic table of elements (Al,13) and the most abundant of all of Earth’s metals, it is very flexible and melts at a low temperature
Alluvial: deposits of clay, silt, sand and gravel left by flowing streams in a river valley or a delta
Amesite: magnesium, aluminum, silicon hydrogen oxygen; a product of low grade metamorphism of aluminum, magnesium-rich rocks, a phyllosilicate, layered or sheet, mica-like, in the serpentine group
Ametrine: a natural occurring variety of quartz that is a mixture of purple amethyst and yellow citrine in one
Amorphous: having no definite form, shapeless like a cloud
Anisotrophic: lacking consistent hardness on all surfaces or asymmetry of crystal layers or direction
Apatite Group: represents the phosphate minerals; chlorapatite, fluoapatite and hydroxyl apatite. These minerals may often replace one another, the most common being fluorapatite
Aqueous Solutions: a solution in which water is the solvent, such as minerals that are dissolved in water
Asbestos: a natural occurring mineral which crystals form long, thin fibers that are resistant to heat
Asterism: is a star effect in certain minerals caused by light traveling perpendicular to the crystal faces along tiny fiber-like inclusions, some stones have four faces such as black star dioptase and some have six like star ruby
Asymmetry: the absence of symmetry, not equal sided or balanced
Atom: the smallest particle that is characterized as a chemical element
Augite: a crystal that consists of (calcium magnesium iron silicate) found in igneous and metamorphic rock
Aventurecense: a metallic, glitter effect seen in certain stones caused by minute mineral platelets within the stone
Banding: a layering of colors or shades within a stone due to the way in which the formation grew, such as malachite, azurite, some agates and chalcedony
Barium: a chemical element (Ba,56) silvery, metallic, alkaline metal not found alone but with other minerals
Beryl Group: (beryllium aluminum silicate) Forms as a six sided crystal. Members are emerald (green), aquamarine (aqua), morganite (pink), heliodor (yellow), bixbite (red)
Beryllium: a member of the periodic table of elements (Be,4), steel gray, light weight, yet brittle, alkaline earth metal. Used as a harden in alloys
Boron: a member of the periodic table of elements and a trivalent nonmetallic element which occurs abundantly in the evaporative ores borax and ulexite. It is also an important element for plant and animal life
Borosilicate: (silica boron oxide) a form of glass
Botryodial: a mineral formation, translucent or opaque, which has a surface texture that resembles a bunch of grapes or smooth bubbles
Cabochon: a lapidary term used to describe a stone that has been cut with a convex top and a flat bottom
Calcite: (calcium carbonate) a common mineral in the Earth’s surface forming in sedimentary rocks and metamorphic limestone, occurring in veins, deposits and as stalactites and stalagmites
Calcium: a member of the periodic table of elements (Ca,20), and a common alkaline earth metal which is essential for all living organisms
Carbon: a member of the periodic table of elements (C,6) and the non metallic basis of all known life
Carbonate: a salt or ester of carbonic acid, carbonate minerals are those containing the carbonate ion
Calibrated: a lapidary term referring to accepted standardized measurements or sizes of cut stones
Cavities: open pockets within a rock or mineral deposit that allow the collection of other elements and water to then be able to form into another formation over time, such as drusy crystals
Chatoyant: an optical reflecting effect found in certain gemstones which have a fibrous, inclusion structure that displays a silky sheen
Chert: a fine grained, silica-rich, cryptocrystalline, sedimentary rock and a form of quartz, the name jasper is used for the more vivid colors of chert, aventurine is also a for of mica rich chert
Chlinoclore: a member of the chlorite group of phyllosilicates (magnesium iron aluminum silicate hydroxide) formed in metamorphic rock
Chlorine: a member of the periodic table of elements (Ci,17), in the salt forming halogen series and the most abundant dissolved ion in ocean water
Chlorite Group: a group of phyllosilicate minerals formed in a wide range of pressure and thermal conditions in metamorphic, igneous and sedimentary rock
Chlorovanadite: a compound of 73.15% lead,10.79% vanadium,13.56% oxygen and 2.5% chlorine
Chromium: a member of the periodic table of elements (Cr,24), which is steel-gray, lustrous, malleable, hard metal with a high melting point
Cobalt: a member of the periodic table of elements (Co,27) and a silver-gray metal found in various ores. It is used in high strength alloys and in pigments, paints and varnishes
Colloidal: a mixture of particles dispersed in two separate phases; a dispersed phase and a continuous phase, the dispersed phase is distributed evenly throughout the continuous phase
Columnar: similar to fibrous, long, slender prisms often with parallel growth
Contact Metamorphous: typically occurs around intrusive igneous rock as a result of temperature increase caused by the intrusion of magma into cooler rock
Continental Plates: The Earth’s crust and mantle are in constant motion, pulling apart, colliding together, moving sideways, causing valleys, mountains rifts, folds and fault lines. Over time this has moved and shaped the continents. There are 14 main plates with smaller sub plates.
Copper: a member of the periodic table of elements (Cu,29) and a valuable element for plant and animal life, a malleable metal with excellent electrical conductivity and also used as an alloy to strengthen other metals
Cordierite: (magnesium aluminum silicate) also known as iolite, a blue-violite translucent to transparent mineral
Corundum: a crystalline form of aluminum oxide and a rock forming mineral, occurring as a mineral in mica schist, gneiss and some marbles in metamorphic terrains, naturally clear but when certain impurities are present it can also be known as ruby or sapphire, with a hardness of 8-9 the clear variety is commonly used as an abrasive for items such as sand paper etc.
Crocidolite: naturally occurring long fine crystal fibers (known as asbestos) which are the basis of the pseudomorh chalcedony known as tiger eye (brown) and hawk eye (blue), the mineral fibers are silicified (replaced by quartz-silica)
Crusts: minerals that form on the surface of a host rock in layers, these layers can have a crystal or botryoidal habit
Crystal: a body that is formed by the solidification of a chemical element, compound or a mixture and has a regularly repeating internal arrangement of its atoms and often external plane faces
Crystalline: rocks that display a definite crystal orientation
Crystallization: the process by which liquid, elemental, mineral solutions are replaced over time by a solid formation
Crystallographic: the scientific study of crystals. Determining the arrangements of atoms in crystals through the analysis of the defraction patterns from a light beam source
Cryptpcrystalline: crystals that are so minute that they can only be seen through a microscope
Deposits: the natural laying down or accumulation of minerals and elements over time which leads to a large body of ore
Dolomite: (calcium magnesium carbonate) found in sedimentary rock of a limestone base
Drusy: a crystal formation that grows as a crust or cavity filling and has very small crystals packed close together like grains of sugar on the surface of the host rock. These formations have allot of sparkle and can be found in a wide range of color, hardness and mineral composition
Element: a chemical element is a type of atom that is defined by its atomic number, which is the number of protons in its nucleus
Emerald: (beryllium aluminum silicate) A member of the beryl family, the green coloring is due to trace amounts of chromium
Encrusted: a type of formation in which minerals grow in a layer over the surface of a host rock or inside of a cavity or vein within a host rock
Enhancement: there are many gem enhancement classifications used today to improve and even design colored gemstones; bleaching, coating, dying, filling heat treating, impregnation, irradiation, diffusion, lazering and waxing
Fabrication: the method of building jewelry by hand from metal sheet and wire with many different gages (thickness) and shapes; flat, round, square, triangular, beaded, etc.
Faceted: a method of cutting transparent or translucent gemstones that produces flat surfaces on geometric shapes a very precise activity done on a faceting machine over a period of several hours
Feldspar: (aluminum, silicate, sodium, potassium, iron, calcium, barium) Found in varying combinations of these elements and the most abundant group of minerals found in Earth’s crust mostly in igneous rock like granite and in metamorphic and sedimentary rock having a wide use in industrial applications today such as glass ware, earthenware, floor tiles, etc.
Feldspathoids: a group of aluminosilicate minerals similar in composition to feldspars but having a lower silica-alkali ratio or containing chloride, sulfide, sulfate or carbonate, specific to igneous rock
Fibers / Fibrous: minerals constructed of fine, usually parallel threads or fibers which can be very flexible, many mineral fibers are changed over time due to heat, silification or pressure and form a chatoyant effect within a specimen
Flaw: an imperfection in physical form or structure, such as a mineral inclusion, crack or weakness
Flintknapper: An individual who shapes flint or other stones for the purpose of making a weapon or tool is a flintknapper. A hard stone (hammer stone) is used to shape another stone that has a particular way of fracturing. Each blow causes a piece to flake away revealing a very sharp edge until the desired shape and size is achieved.
Fluorine: a member of the periodic table of elements (F,9) and the most electronegative of all of the elements, a pale yellow-brown gas which is poisonous and can cause burns only in its purist form, as a mineral specimens it is not harmful
Fool’s gold: (iron sulfide) The mineral iron pyrite with its metallic, brass-yellow color can sometimes resemble gold
Formation: in geology referring to the types of rock formations such as; igneous, sedimentary and metamorphic. In smaller rocks or crystals it refers to the individual classification and character of any given specimen and the way it presents itself
Fossil: mineralized preserved remains of animals, plants and other organisms found in rock formations and sedimentary layers allowing for the study of geological time
Fracture: In crystalline materials, individual crystals can fracture without the body actually separating. Fracture planes can be a natural part of a formation or specimen. The cleavage of a stone is a result of the natural way in which it will fracture.
Gama-Ray Irradiated: a form of electromagnetic radiation or light emissions of a specific frequency produced from subatomic particle interaction, gamma rays release electrons from their normal location in the gemstone, the color change depends on where the electrons relocate and on the charge of the atoms near them, this controls the way the stone absorbs light and that dictates its color
Garnet Group: almandine-deep red (iron aluminum silicate); andradite-red, green, yellow, brown, black (calcium iron silicate); grossular-clear, white, green, yellow,pink, brown, orange and orange-red (calcium aluminum silicate); pyrope-deep red to almost black (magnesium aluminum silicate); spessartine-brown, orange and pink (manganese aluminum silicate); uvarovite-green (calcium chromium silicate)
Gem: a precious or semiprecious stone cut and polished for ornament
Gemstone: a mineral or petrified material that can be cut, polished and set into jewelry
Gemology: the science of identifying and evaluating gemstones
Geode: A geode rock formation usually has an internal cavity lined with crystals or filled with a banded, lacy mineral body or a botryoidal formation. The outside of the geode is usually limestone or related rock and the interior contains quarts crystals or chalcedony deposits. A geode is cut in half to display the interior. Some specimens that have a drusy formation are cut into individual stones and set into jewelry.
Geology: a science that studies the structure of the Earth and the forces that shape it, including composition, structure, physical properties and geological processes
Gneiss: a common type of rock that forms from grains of preexisting igneous or metamorphic rock in bands or layers (foliated) and re-crystallized by metamorphic process
Goethite: (iron oxide) Brown iron ore found in many types of formations and environments worldwide
Gold: a member of the periodic of elements (Au,79) and a highly valued precious metal that occurs as nuggets, grains and veins in rocks and in alluvial deposits such as creaks and washes, It is a soft, malleable and bright yellow
Grainy Masses: a mineral, crystalline aggregate, rough or fine grained such as granite
Granite: a common, widely occurring, intrusive, igneous rock of hard, grainy, crystalline, texture, consisting of quartz and orthoclase or microcline
Granular: organic or inorganic material that has a small particle size such as grains of sand
Habit: the growth conditions and characteristic features of a rock or crystal formation
Hardness: each crystal, mineral or stone has its own hardness, determining the hardness of a stone is done by the scratch method used in the Mohs Scale, a harder material will scratch a softer material
Heat Treatment: used to lighten, darken or alter a stones color
Hydrated: In inorganic chemistry hydrates contain water molecules that are bound to a metal center or crystallized with the metal complex.
Hydrocarbons: In organic chemistry a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon.
Hydrogen: a member of the periodic table of elements (H,1) and an odorless, colorless, nonmetallic, tasteless, and highly flammable, diatomic gas, It is the lightest and most abundant element in the Universe
Hydrothermal: the transport and circulation of water deep within the Earth’s crust from hot areas to cool areas, such as hot springs or geysers or when hot magma comes in contact with groundwater
Hydrous: chemically combined with water in crystallization
Hydroxide: consisting of oxygen and hydrogen atoms
Hydroxyl: an oxygen atom and a hydrogen atom connected by a covalent bond (a form chemical bonding that is characterized by the sharing of pairs of electrons between atoms)
Igneous Rock: rock that forms as a result of volcanic activity, below the surface as intrusive or on the surface as extrusive, this magma can be derived from preexisting rock beneath the surface of the Earth’s crust
Impurities: In mineralogy impurities are the different minerals and chemical elements that give a rock or crystal its color.
Inclusions: In gemstones inclusions are smaller minerals or mineral fibers that are imbedded within the specimen.
Inlay: a form of stone cutting and setting in jewelry in which stones are cut to fit exactly into a channel or compartment, then the stones are set in place with strong epoxy and the surface of the stones and the metal are both sanded down to a flush finish
Intrusive Rock: an igneous rock formation that forms below the surface of the Earth as a result of molten magma flows, it solidifies before it reaches the surface and may or may not be crystallized
Inorganic: composed of matter other than plant or animal
Iridescence: a play of colors producing a rainbow effect or hue change on a surface when viewed from different angles caused by multiple reflections from multi layered, semitransparent surfaces
Iron: a member of the periodic table of elements (Fe,26), a heavy malleable, ductile, magnetic metal, chiefly found in igneous rock and the heaviest, most widely used metal
Iron Oxide: forms as a result of iron being exposed to the oxygen in the atmosphere
Kimberlite: potassium-rich volcanic rock occurring in the Earth’s crust and known for containing diamonds, named after the town of Kimberly, South Africa where the diamond rush of 1871 began
Knobby Swirls: some rock formations grow with bubbly-knobby (botryoidal) and banded swirls together, suck as azurite and malachite
Labradorescence: an iridescent sheen, color display or optical phenomenon present in labradorite and caused by feldspar minerals, colors change as the stone moves
Lacing: as in lace agate, crystalline layers form one on another and the effect is the look of old fashioned lace
Lead: a member of the periodic table of elements (Pb,82) and a soft, heavy, toxic and malleable poor metal, found in copper, silver and zinc deposits
Limestone: a sedimentary rock composed largely of the mineral calcite
Lithium: a member of the periodic table of elements (Li,3) and a soft silver-white alkali metal, the lightest and least dense metal and occurs in pegmatite minerals
Luster: the way light interacts with the surface of a crystal, rock or mineral in radiance, gloss or brilliance
Macrocrystalline: having crystals large enough to be seen with the unaided eye
Mafic: dark colored ferromagnesian minerals such as pyroxene and olivine
Magnesium: a member of the periodic table of elements (Mg,12) and an alkaline earth metal essential to all living cells, a silvery-white, lightweight metal, found in over sixty minerals, dolomite, magnesite, brucite, talc, carnallite and olivine are of commercial importance
Manganese: a member of the periodic table of elements (Mn,25) often found in combination with iron as well as many minerals, a required trace mineral for all living organisms
Mantle: the region of the Earth’s interior between the crust and the core, which contains hot, dense silicate rocks, 1,800 miles thick and is 70% of the Earth’s volume
Marble: a metamorphic rock which forms as a result of metamorphism of limestone which is mostly calcium carbonate or dolostone (dolomite), different minerals give marble its different colors, formed under intense heat and pressure
Massive: shapeless, no distinctive external crystal shape
Metamorphic Rock: makes up a large part of the Earth’s crust and is formed under the surface in high temperatures and under great pressure
Mica: sheet silicate
Mica Group: group of sheet silicate minerals; true micas, brittle micas and inter layered-deficient micas, this combination of minerals is too numerous to mention here
Mica-Schist: a metamorphic silica-rich rock, most commonly containing aluminum and potassium, forms in thin flaky sheets as a result of preexisting igneous and sedimentary rock being altered again by heat and pressure
Microcline: a potassium-rich, alkali feldspar, formed in igneous rock of granite and pegmatites, amazonite is a green variety of microcline
Microcrystalline: a small, fine crystal structure that is only visible through a microscope
Minerals: a naturally occurring substance formed by geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties
Mineral Fibers: aggregate minerals constructed of fine, parallel threads compacted together, some specimens have a cloth-like flexibility often compacted together under heat and pressure and silicified as in the case of crocidolite asbestos which forms the mineral tigereye, rutile is also another example
Mohs Scale: a scale used to determine the hardness of a mineral in which a scratch test is used, a harder material is used to scratch a softer material, created in 1812 by Frederich Mohs. Talc has a hardness of 1 and diamond a hardness of 10
Molybdate: a compound containing an oxoanion (a negatively charged poly atomic ion that contains oxide)
Molybdenum: a member of the periodic table of elements (Mo,42) and has a very high melting point and is used in high strength steel alloys, found in trace amounts in plants and animals
Muscovite: also known as common mica and a phyllosilicate of aluminum and potassium, found in granites, pegmatites, gneiss and schists and as a contact metamorphic rock, the green chromium-rich variety is called fuchsite
Nickel: a member of the periodic table of elements(Ni,28) and a silvery, white metal which is hard and ductile, used in coins, for plating brass and iron and as a high performance alloy
Nitrogen: a member of the periodic table of elements (N7) and a colorless, odorless, unreactive gas that forms about 78% of the Earth’s atmosphere
Olivine: known also as peridot (magnesium iron silicate) and found in lava fields worldwide and in meteorites
Opaque: non transparent or translucent; impermeable to light; not allowing light to pass through
Ore: the earthen-material or “mother rock” that holds valuable elements, minerals or metals in deposits in the Earth’s crust, which is extracted in the mining process
Organic: matter that comes from a recently living organism which is subject to decay, an organic compound whose molecules contain carbon
Orthoclase: an important, tectosiliicate mineral also known as feldspar which is common in pegmatite, igneous, granite and has a monocline crystal structure and a straight cleavage, potassium and sodium are important minerals in these formations
Overlay: in jewelry fabrication, it is the process of soldering a special design sheet of metal over another, such as a textured or cut out design in gold over silver
Oxide: a chemical compound containing an oxygen atom and other elements, oxides result when elements are oxidized by air, most of the Earth’s crust consists of oxides
Oxidation: a chemical reaction that occurs when a metal, such as iron, meets a gas such as oxygen; the result being rust, oxidation is the transfer of electrons from the metal to the gas
Pegmatite: a coarse-grained igneous rock that has a grain size of 20 mm or more and which consists of quartz, feldspar and mica which all form granite
Periodic Table of Elements: a tabular method of displaying the chemical elements credited to Russian chemist Dmitri Mendeleev in 1869 and used to classify, systematize and compare the many forms of chemical behavior
Petrified: a condition in which all organic materials, within a structure, have been replaced with minerals (most often a silicate such as quartz), while retaining the original structure
Phosphate: in inorganic chemistry, it is a salt of phosphoric acid
Phosphoric Acid: an inorganic mineral acid, also known as orthophosphoric acid or phosphoric (V0) acid
Phosphorus: a member of the periodic table of elements (P,15) and a multivalent nonmetal of the nitrogen group found in inorganic phosphate rock and an essential element for all living cells, phosphorous compounds are also used in explosives, detergents, fertilizers, fireworks, matches, pesticides and toothpaste
Phyllosilicate: the formation of silica sheets that grow in layers and are held together with a weak bond that allows them to flake apart easily, this includes mica, talc, clay minerals and muscovite
Plagioclase: within the felspar family it is an important tectosilicate series of minerals which has two cleavage angles. Sodium and calcium are important minerals in its structure which originates from igneous rock.
Placer: a deposit of sand or gravel in the bed of a river or lake, containing particles of valuable material such as gold or diamonds
Plechorism: an optical phenomenon in which a stone will appear to have different colors when observed at different angles as when light travels on different paths and at different speeds on the crystal plains, there will be polarizations, each with there own color
Polymorph: the ability of a material to exist in more than one form or crystal structure
Potassium: a member of the periodic table of elements (K,19), and a soft silvery-white, metallic, alkali metal that occurs naturally bound to other elements and sea water
Pseudomorph: a mineral compound in which the main component is substituted for another while keeping its original appearance and dimensions
Pyrite: iron pyrite is iron sulfide and its crystals form as shinny, brass-gray cubes, often referred to as “Fool’s Gold”
Pyrope: a type of garnet in the garnet family (magnesium aluminum silicate), which ranges in color from fire-red, deep red, violet-red to almost black
Quartz Family: Silicon and oxygen are the two most common elements in the Earth’s crust thereby making the quartz family the largest of all groups. Silicon dioxide forms as amethyst, ametrine, citrine, rose quartz, smokey quartz, chalcedony, agate, onyx, sardonyx, carnelian, chrysoprase, chert, aventurine, jasper and tigereye.
Radiating Cluster: a crystal of any variety that grows in a radiating formation in which the crystals start at one point and fan out in all directions, they can be flat or three dimensional and there can be one or several clusters within a specimen
Radiation: the emission of energy as electromagnetic waves or as moving subatomic particles, especially high-energy particles that cause ionization; heat, light, electricity, etc.
Radium: a member of the periodic table of elements (Ra,88), and a radioactive element and an alkaline earth metal that is found in trace amounts in uranium ore
Refractive Index: the measure of the bending of a ray of light when passing from one medium to another
Rhyolite: a silica-rich, igneous, extrusive rock formed in highly viscous lavas that have cooled more slowly consisting mostly of quartz, alkali feldspar and plagioclase feldspar
Riebeckite: dark blue elongated fibrous crystals found in granites, syenites, schists and iron formations known as crocidolite which is blue asbestos
Rock: a natural occurring aggregate of minerals which can be formed by igneous, sedimentary or metamorphic processes
Rubellite: one of the six members of the tourmaline group which has a pink color due to manganese
Ruby: a pink or red variety of corundum, aluminum oxide, with chromium giving it its pink or red color, the most valuable stones have the deepest red color and a presence of some mineral fibers is of value as proof of non treatment (heat treatment), a hardness of 9 on the Mohs scale, see corundum above
Rutile: a mineral fiber composed mostly of (titanium dioxide) which can grow on the inside or the outside of another mineral or crystal (an accessory mineral) formed in high pressure and high temperature metamorphic and igneous rock
Schist: a group of metamorphic rocks derived from clays, muds, silts and fine grained igneous rock and containing foliated minerals such as mica, talc, and graphite
Sediment: any particulate matter that can be transported by fluid flow and which is later deposited as a layer of solid material, it can also be a result of particles settling after they are suspended in a still body of liquid
Sedimentary Rock: Sedimentary rock shows the record of the history of the surface of the Earth. As layers of silt, sand, gravel and boulders, usually from silicate minerals, are laid down from rivers and streams, conglomerate layers are formed. As lakes and oceans evaporate they leave behind minerals, microscopic sea life and fossils. Limestone, shale, dolomite and sandstone are the result. Volcanic activity, climate and atmosphere have also contributed to the formation of sedimentary rock.
Shale: a fine-grained sedimentary rock made of clays, muds and silts
Sheen: a glossy, glistening or satiny surface
Sheet Silicates: also called phyllosilicates (phyllo means leaf like), these minerals form in thin sheets or layers such as mica and talc
Shiller: an optical color effect seen in a stone which is caused by a ray of light entering a layer and being refracted back and forth by deeper layers within the stone, as the wavelength travels it changes speed and the resulting color is due to the thickness and the orientation of the layers in the stone
Silica: silicon dioxide
Silica Group: group of silicate minerals composed only of silicon dioxide such as; quartz, agate, chalcedony, onyx, carnelian, chrysoprase, tiger eye, sardonox, citrine, amethyst, ametrine, rose quartz, smokey quartz etc.
Silicate: Silicate minerals are those containing silicon dioxide. The largest class of minerals composing 90% of Earth’s crust. Approximately 30% of all minerals are silicates.
Silicic: magma or igneous rock rich in silica, granite and rhyolite are typical silicic rock
Silver: a member of the periodic table of elements (Ag,47) and a soft, white, lustrous, precious metal, most silver is a byproduct of copper, gold, lead and zinc mining
Slab / Slabbing: One lapidary term used to describe the process of cutting a stone is slabbing. A rock or crystal is usually first cut open or trimmed on a slab saw before moving on to the grinding process, which forms the basic shape. A slab saw is a thin round flat disc of steel that is used with water or other cooling lubricants. The rim of the blade is embedded with diamond grit.
Smithsonian National Museum of Natural History; Department of Mineral Sciences Collections: The National Gem and Mineral Collection is one of the most significant collections of its kind in the world. The collection includes some of the most incredible gems and minerals ever found. There are over 375,000 specimens in the museum as well as a research collection used by scientists around the world.
Sodalite: (sodium aluminum silicate) a feldspathoid well known for its deep, royal, blue color and sodium content, found in Canada and Greenland and has a hardness of 5.5-6 on the Mohs scale
Sodium: a member of the periodic table of elements (Na,11) and a soft, white, highly reactive element, an alkali metal which quickly oxidizes in air and is abundant in the Earth, a component of many minerals and it is also an essential element for animal life
Sorosilicate: any member of a group of compounds with structures that have two silicate tetrahedrons (a central silicon atom surrounded by four oxygen atoms at the corners of a tetrahedron) linked together, because one oxygen atom is shared by two tetrahedrons, the chemical formula contains Si207, as in hemimorphite
Specimen: In geology a specimen refers to any particular item or part typical of the whole. As a gem, crystal or mineral a specimen can be a sample of the whole of the mineral world or an example of a particular category.
Stalactite: a mineral formation that develops inside of a cavern over a long period of time due to mineral-rich water that drips from the ceiling, the dissolved minerals slowly accumulate into an icicle-like formation
Stalagmite: a mineral formation that develops inside of a cavern over a long period of time due to mineral-rich water that drips from the ceiling onto the floor, as the minerals collect, crystallize and build over time the formation resembles a stack or tower
Strontium: a member of the periodic table of elements (Sr,38) and an alkali earth metal, it is a soft, silver-white or yellowish, metallic element that is highly reactive chemically
Sulfate: a salt of sulfuric acid
Sulfide: Most major ores of important metals such as copper, lead and silver are sulfides. They are also soft to medium in hardness, opaque, metallic and igneous in origin. These metallic elements combine with sulfur (which then acts as a semimetal) to form sulfides.
a member of the periodic table of elements (S,16) and an abundant, tasteless, multivalent, nonmetal and a yellow crystalline solid essential element for plant and animal life
Syenite: a coarse-grained, intrusive, igneous rock of the same general composition as granite but with quartz being absent or present in very small amounts, mostly orthoclase, alkaline feldspar with aluminum being an important element
Table of Elements: a tabular method of displaying the chemical elements, invented in 1869 by Dmitri Mendeleev to illustrate recurring (periodic ) trends in properties of the elements, the table has been refined and even extended over time as new elements have been discovered and with better understanding of how chemical elements behave
Tabular Crystals: flat tablet shaped habit of growth
Tectosilicates: also called “framework silicates” because their structure is composed of interconnected tetrahedrons (four faced triangles) going outward in all directions forming an intricate framework with their oxygen atoms at each corner, almost 75% of the Earth’s crust is composed of minerals with this three-dimensional framework
Tetrahedron: a shape composed of four triangular faces thereby giving it four points at which these faces meet
Titanium: a member of the periodic table of elements (Ti,22) and a light, strong, lustrous, corrosion-resistant, transition metal with a white-silvery metallic color which has the highest strength-to-weight ratio of any metal and is found in almost all living things, rocks, water bodies, and soils
Titanium Dioxide: a naturally occurring oxide of titanium which is used as a pigment in paints
Tourmaline Group: The eleven members of this group display a large variety of colors, including red, orange, yellow, green, blue, violet, white, gray, black and brown. Species of this group crystallize in the hexagonal system and are usually elongated prisms, sometimes stubby or with different terminations on each end of the crystal. Formed in igneous, metamorphic and sedimentary rock.
Translucent: the ability to see light through a stone
the ability to see clearly through a stone
Tucson Gem and Mineral Show: The show is a yearly gathering of gem, fossil and mineral dealers from around the world held in Tucson Arizona for two weeks in the month of February. It grows more each year and vendors cover a vast portion of the city bringing multiple millions of dollars into the community.
Tungsten: a member of the periodic table of elements (W,74) and a very hard, heavy, steel-gray to white transition metal with the highest melting point of all non-alloyed metals, the second highest of all elements after carbon and a super alloy with broad applications
Ultrmafic: igneous rocks composed of mafic materials
Vapor Coating: a technique used to deposit a thin film one atom (or molecule) at a time onto the surface of a stone, used on clear stones to give a colorful rainbow effect
Veins: a long narrow opening or crack in a rock formation or an ore deposit that fills with water and minerals and over time crystallizes into another mineral or crystal formation
Verdelite: green tourmaline in which its coloring is due to chromium
Vitreous: glasslike in appearance
Vug: a cavity in rock lined with mineral crystals
Zinc: a member of the periodic table of elements (Zn,30) and a moderatley-reactive, bluish-white metal that tarnishes in moist air, when burned it gives off plumes of zinc oxide

Glossary of Geological Words and Terms compiled and written by Marilyn Mack in her own words as a complement to Geological Information, Specimen Content and Origin Page


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