Copy of `Inland Lapidary - Gem glossary`
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Inland Lapidary - Gem glossary
Category: General technical and industrial > Gems and Geology
Date & country: 27/10/2013, USA
Words: 1119
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striation 1.) One of a group of usually parallel scratches engraved in bedrock by a glacier or other geological agent. 2.) Tiny, parallel lines seen on some crystal faces.
strike 1. ) The horizontal line marking the intersection between the inclined plane of a solid geological structure and the Earth's surface. 2. The compass direction of this line, measured in degrees from true north.
strike-slip fault A fault in which two sections of rock have moved horizontally in opposite directions, parallel to the line of the fracture that divided them. Strike-slip faults are caused by shearing stress.
structural geology The scientific study of the geological processes that deform the Earth's crust and create mountains.
structure 1.) The form of a mineral based on the way its molecules are arranged. 2.) Features exhibited in rock portions, for example flow banding and bedding.
stubby Short and fat. Used in describing crystals.
stud Small jewel placed on an ornament, such as an earring. May also refer to the verb form of setting with a stud. Sometimes additionally refers to a cable that holds together a metallic ornamental chain, such as a necklace.
sub metallic subconchoidal fracture Mineral fracture that falls somewhere between conchoidal and even; being smooth with irregularly rounded corners.
subduction The sinking of an oceanic plate edge as a result of convergence with a plate of lesser density. Subduction often causes earthquakes and creates volcano chains.
subgroup The next level of mineral classification after categorization in groups.
sublimate To go from a solid state directly to a gaseous state without becoming liquid.
subsidence The lowering of the Earth's surface, caused by such factors as compaction, a decrease in groundwater, or the pumping of oil.
sulfates Group of minerals that contains one or more metallic element in addition to the sulfate radical (SO
4). All sulfates are transparent to translucent and soft. Most are heavy and lightly colored, and some are soluble in water. Rarer sulfates exist containing substitutions for the sulfate radical, such as the chromates, where it ...
sulfides Group of minerals that are compounds of one or more metallic elements combined with the non-metallic element sulfur. The sulfur acts as a semi-metal when it combines to form a sulfide mineral. In some sulfides, the semi-metals arsenic, antimony, selenium, and tellurium substitute for the sulfur. There are different types of sulfides known as: Simpl...
sulfosalts Group of sulfides that contain one or more true metals, sulfur, and either the semi-metals antimony, arsenic, or bismuth. They are generally soft, have a metallic luster, and are heavy and uncommon.
sulfuric acid Chemically H
2SO
4, it is a corrosive, oily, acid used for manufacturing chemicals, medicine, paints, detergents, and explosives. It is a very destructive liquid and will destroy many minerals.
surface wave One of a series of seismic waves that transmits energy from an earthquake's epicenter along the Earth's surface. See also body wave.
surge To flow more rapidly than usually. Said of a glacier.
surrounding rock The rock surrounding a vein or embedded crystal.
suspended load A body of fine, solid particles, typically of sand, clay, and silt, that travels with stream water without coming in contact with the stream bed.
suture zone The area where two continental plates have joined together through continental collision. Suture zones are marked by extremely high mountain ranges, such as the Himalayas and the Alps.
swallowtail twin Form of penetration twinning in which two monoclinic crystals twin to form a v-shaped model, as depicted in the figure below. This form of twinning is most frequently seen on the mineral Gypsum.
syenite Igneous rock containing alkali feldspars. Contains mica and pyroxene minerals.
symmetry Exact proportion from an intermediate center horizontal line, vertical line, or central point. If an object has symmetry, than it can be rotated or flipped and appear the the exact same way it was before the rotate or flip. The axes (x axis and y axis) are imaginary lines drawn through the center of the shape; the x axis going in a horizontal direc...
syncline A concave fold, the central part of which contains the youngest section of rock. See also anticline.
tabular Crystal habit describing a flat, tough, usually four sided crystal.
talus A pile of rock fragments lying at the bottom of the cliff or steep slope from which they have broken off.
talus slope The large pile of rocky boulders that accumulates at the foot of a cliff, typically by the mechanical-weathering process of frost-wedging.
tarn A deep, typically circular lake that forms when a cirque glacier melts.
tarnish Property in certain minerals that cause them to discolor when placed in certain environments. A famous example is Silver, which develops a yellowish-black coating on its surface when exposed to hydrogen sulfide (H
2S), which is present in small quantities in the atmosphere.
tectonic creep The almost constant movement of certain fault blocks that allows strain energy to be released without major earthquakes.
tectosilicates Group of silicate minerals that have all four oxygen atoms from each tetrahedron share itself with an adjacent tetrahedron.
tellurides subgroup Group of sulfides that contain one or more true metals combined with the semi-metal tellurium.
tenacity The reaction of a mineral to certain stress.
tenebrescence The property that some minerals and phosphors show or darkening in response to radiation of one wavelength and then reversibly bleaching on exposure to a different wavelength. This phenomenon is also called reversible photochroism.
tension Stress that stretches or extends rocks, so that they become thinner vertically and longer laterally. Tension may be caused by divergence or rifting.
tephra (plural noun) Pyroclastic materials that fly from an erupting volcano through the air before cooling, and range in size from fine dust to massive blocks.
termination The end of a crystal face, usually referring to its base.
terminus The outer margin of a glacier.
tetragonal crystal system Any mineral that falls under the following specifications belongs to the tetragonal crystal system: Three axes, two are equal in length, one is unequal. All three axes are at 90� to each other.
tetragonal trisoctahedron Synonym of trisoctahedron.
tetrahedral Exhibiting the shape of a tetrahedron.
tetrahedron 1. Four sided polyhedron; all sides are equidimensional and triangular shaped. Minerals shaped as tetrahedrons belong to the isometric system. 2. The building block of all silicates. It is composed of one silicon atom equidimensionally placed around four oxygen atoms. The groups of silicates are classified based on how the tetrahedrons join togethe...
texture The feel and appearance of a mineral, such as color, crystal form, and luster.
theory A comprehensive explanation of a given set of data that has been repeatedly confirmed by observation and experimentation and has gained general acceptance within the scientific community but has not yet been decisively proven. See also hypothesis and scientific law.
thermal contraction A form of mechanical weathering in which cold causes a mineral's crystal structure to contract.
thermal expansion A form of mechanical weathering in which heat causes a mineral's crystal structure to enlarge.
thermal plume A vertical column of upwelling mantle material, 100 to 250 kilometers in diameter, that rises from beneath a continent or ocean and can be perceived at the Earth's surface as a hot spot. Thermal plumes carry enough energy to move a plate, and they may be found both at plate boundaries and plate interiors.
thermoluminescence Phenomenon exhibited in certain minerals that they give off light, like a glow, when heated. Can only be observed in a dark area. Thermoluminescent is term used to describe minerals that emit light after being heated.
thrust fault A reverse fault marked by a dip of 45� or less.
tidal bore A turbulent, abrupt, wall-like wave that is caused by a flood tide.
tide 1. The cycle of alternate rising and falling of the surface of an ocean or large lake, caused by the gravitational pull of the Sun and especially Moon in interaction with the Earth's rotation. Tides occur on a regular basis, twice every day on most of the Earth. 2. A single rise or fall within this cycle.
topography The set of physical features, such as mountains, valleys, and the shapes of landforms, that characterizes a given landscape.
transform motion The movement of two adjacent lithospheric plates in opposite directions along a parallel line at their common edge. Transform motion often causes earthquakes.
transformation The alteration of one mineral to another.
translatory motion the movement of water over a significant distance in the direction of a wave.
translucent Describing something that is able to transmit light but not fully. Objects can be seen through a translucent object, but they will be unclear.
transparency The quality of how a mineral lets light through.
transparent Describing an object that is able to transmit light through it, and if placed in front of another object, that object can be seen as if there is nothing interfering.
transverse dune One of a series of dunes having an especially steep slip face and a gentle windward slope and standing perpendicular to the prevailing wind direction and parallel to each other. Transverse dunes typically form in arid and semi-arid regions with plentiful sand, stable wind direction, and scarce vegetation. A transverse dune may be as much as 100 kil...
trap rock Rock formed from solidified lava, which usually contains pockets holding crystals.
trapezohedral Shaped as a trapezohedron.
trapezohedran Synonym of trisoctahedron.
tributary A stream that supplies water to a larger stream.
trichroic Synonym of pleochroic.
triclinic crystal system Any mineral that falls under the following specifications belongs to the triclinic crystal system: Three axes, all of them are unequal in length, none of them are right angles to each other.
trigonal crystal system The trigonal crystal system is really part of the hexagonal crystal system and only has one minute difference (in that true hexagonal minerals have sixfold symmetry, whereas trigonal minerals have threefold symmetry). The trigonal crystal system, like the hexagonal crystal system, has: four axes, three are equal in length and lie at an angle of 120...
trilling Intergrowth of three orthorhombic crystals that twin at the center and form a hexagonal shaped crystal.
triplet Gem composed of three cross-sections pasted together. The top portion, which is the portion that is visible, consists of a naturally occurring, valuable gem, while the bottom two portions are low-grade material, such as glass or rock crystal.
trisoctahedron 24 sided polyhedron; all sides are equidimensional. Minerals shaped as trisoctahedrons belong to the isometric system and are referred to as trisoctahedral.
trunk An individual portion of a vein.
trunk stream A large stream into which tributaries carry water and sediment.
tsunami tsunami) A vast sea wave caused by the sudden dropping or rising of a section of the sea floor following an earthquake. Tsunami may be as much as 30 meters high and 200 kilometers long, may move as fast as 250 kilometers per hour, and may continue to occur for as long as a few days.
tube test Complex, scientific test which is conducted to identify a mineral. A mineral is crushed and its powder is placed in an open or closed tube, which is then heated; the reaction of the powder in the tube to the heat acts as a guide for identifying the presence of certain metals in the mineral.
tufa Synonym of sinter: Mineral deposit formed by mineral-rich spring water which comes to the surface and loses its capacity to withhold the dissolved mineral, thereby depositing it and forming a growing mound. Sometimes misconceived as tuff.
tufacious spring Spring which produces tufa.
tuff Porous igneous rock composed of volcanic ash compacted together.
tumbled Having been placed in a tumbler, which smoothes out and enhances the luster of a mineral. Rocks and minerals may be naturally tumbled, if they were smoothed and rounded from having been in a fast-flowing stream or river for a long period of time.
tungstates group Group of minerals that are compounds of one or more metallic elements and the tungstate radical (WO
4). These minerals are very heavy, soft, and brittle. The tungstates are usually categorized with the chemically related molybdates, in which they can be partially replaced by. The tungstates are also known as the wolframates.
ultrabasic Describing an igneous rock containing magnesium and iron with a very low percentage of silica, less than 45%.
ultraviolet light Type of electromagnetic radiation which cannot be seen by humans. Ultraviolet, often abbreviated U.V. is term used when referring to ultraviolet light. Ultraviolet Lamp (U.V. lamp) is one that gives off ultraviolet light while blocking out white light, which causes fluorescent minerals to react.
unconformity A boundary separating two or more rocks of markedly different ages, marking a gap in the geologic record.
uneven fracture Fracture that leaves a rough or irregular surface.
uniformitarianism The hypothesis that current geologic processes, such as the slow erosion of a coast under the impact of waves, have been occurring in a similar manner throughout the Earth's history and that these processes can account for past geologic events. See also catastrophism.
unstable Mineral with a crystal structure that is unable to exist at the current temperature. When certain minerals become unstable, they transform into their paramorphs. Also refers to radioactive minerals which cannot withstand their composition and begin to decay.
upwarped mountain A mountain consisting of a broad area of the Earth's crust that has moved gently upward without much apparent deformation, and usually containing sedimentary, igneous, and metamorphic rocks.
valley glacier An alpine glacier that flows through a preexisting stream valley.
van der Waals bond A relatively weak kind of intermolecular bond that forms when one side of a molecule develops a slight negative charge because a number of electrons have temporarily moved to that side of the molecule. This negative charge attracts the nuclei of the atoms of a neighboring molecule. The side of the molecule with fewer electrons develops a slight pos...
vanadates Group of minerals that are compounds of one or more metallic element associated with the vanadate radical (VO
4). The vanadates, together with the related arsenates, are classified in the phosphate group. Most vanadates are heavy, and none are hard. They are usually brittle and occur in small crystals or compact aggregates.
variable formula Chemical formula of a mineral that includes all common elemental replacements. For example, the mineral Adamite - Zn
2(AsO
4)(OH), frequently contains part of the zinc (Zn) replaced by copper (Cu) or cobalt (Co); thus its variable formula is (Zn,Cu,Co)
2(AsO
4)(...
variety Titled variable of a mineral, characterized by a special property not present in other members of that same mineral such as color, location, chemical additive, crystal or aggregate, etc.
varve A pair of sediment beds deposited by a lake on its floor, typically consisting of a thick, coarse, light-colored bed deposited in the summer and a thin, fine-grained, dark-colored bed deposited in the winter. Varves are most often found in lakes that freeze in the winter. The number and nature of varves on the bottom of a lake provide information a...
vein A long, thin section of a mineral, usually in fibrous form, embedded in rock, called the surrounding rock. Usually caused by the filling in of the mineral in open spaces or cracks in the rock
vent An opening in the Earth's surface through which lava, gases, and hot particles are expelled. Also called volcanic vent and volcano. Venting is The escaping of hot gases or lava from the crust of the earth.
ventifact A stone that has been flattened and sharpened by wind abrasion. Ventifacts are commonly found strewn across a desert floor.
verneuil process The course of creating synthetic gems from molten solutions and letting them form into boules.
viscosity A fluid's resistance to flow. Viscosity increases as temperatures decrease.
vitreous luster Luster describing minerals with reflective properties similar to that of glass.
