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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sedimentary structure A physical characteristic of a detrital sediment that reflects the conditions under which the sediment was deposited.
sedimentation process Process in which sediment transforms into sedimentary rock.
seismic gap A locked fault segment that has not experienced seismic activity for a long time. Because stress tends to accumulate in seismic gaps, they often become the sites of major earthquakes.
seismic moment A numerical means of measuring an earthquake's total energy release. It is calculated by measuring the total length of fault rupture and then factoring in the depth of rupture, total slip along the rupture, and the strength of the faulted rocks.
seismic profiling The mapping of rocks lying along and beneath the ocean floor by recording the reflections and refractions of seismic waves.
seismic tomography The process whereby a computer first synthesizes data on the velocities of seismic waves from thousands of recent earthquakes to make a series of images depicting successive planes within the Earth, and then uses these images to construct a three-dimensional representation of the Earth's interior.
seismic wave One of a series of progressive disturbances that reverberate through the Earth to transmit the energy released from an earthquake.
seismogram A visual record produced by a seismograph and showing the arrival times and magnitudes of various seismic waves.
seismograph A machine for measuring the intensity of earthquakes by recording the seismic waves that they generate.
seismology The study of earthquakes and the structure of the Earth, based on data from seismic waves.
selenides subgroup Group of sulfides the contain one or more true metals combined with the semi-metal selenium.
selvage The area of the point of contact between a vein and the surrounding rock.
semi-metal Element or alloy exhibiting certain properties of the metals and certain properties of the non-metals. They are opaque with a metallic luster, and combine with other elements to form minerals as metals do. In all other aspects, they act like non-metals.
semi-metallic elements The semi-metallic elements are minerals belonging to the native elements group and are composed of pure semi-metallic elements or semi-metallic alloys. They are opaque with a metallic luster, and combine with other elements to form minerals (i.e. Arsenides, Tellurides) the same way the metallic elements do.
semi-precious stone Gem or gemstone used in jewelry but lacks in one or more property (such as luster, hardness, and rarity) that would make it into a precious gemstone.
series A series is a mineral group consisting of minerals that have a nearly identical crystal structure. The only difference between the minerals in a series is the type of elements contained in the crystal structure of the mineral. This means that there must be at least two defined minerals in a series: one mineral containing one particular element, and...
setting The proper placement of a gem on an ornament, or the ordained area for the placement of a gem.
shaft A long, narrow passage in underground mines created for the extraction of valuable material.
shale A sedimentary rock composed of detrital sediment particles less than 0.004 millimeter in diameter. Shales tend to be red, brown, black, or gray, and usually originate in relatively still waters.
sheaflike Synonym to wheat sheaf.
shearing stress Stress that slices rocks into parallel blocks that slide in opposite directions along their adjacent sides. Shearing stress may be caused by transform motion.
sheet silictes Another name for phyllosilicates. Group of silicate minerals that have each set of tetrahedrons surrounded by three oxygen atoms, forming a sheet like structure.
shelly fracture Synonym of conchoidal fracture.
shield volcano A low, broad, gently sloping, dome-shaped structure that forms over time as repeated eruptions eject basaltic lava through one or more vents and the lava solidifies in approximately the same volume all around.
shock metamorphism The metamorphism that results when a meteorite strikes rocks at the Earth's surface. The meteoric impact generates tremendous pressure and extremely high temperatures that cause minerals to shatter and recrystallize, producing new minerals that cannot arise under any other circumstances.
shoreline The boundary between a body of water and dry land.
short wave A wavelength of ultraviolet light. Many minerals display fluorescence when exposed to shortwave ultraviolet light. Commonly abbreviated as SW.
silica Radical of silicon and oxygen. Also term for any material composed of only silicon and oxygen (and can include water), such as Quartz, Chalcedony, and Opal.
silica group Group of silicate minerals (tectosilicates) composed only of silica (silicon dioxide -- SiO2 ). The minerals in this group are all the varieties of Quartz, Chalcedony, Opal, Tridymite, and Cristobalite (and a few rarer forms of silicon dioxide). Although Opal contains water in addition to silica, it is nevertheless in the silica group. The Silica G...
silicafied Having been transformed into silica. An example is petrified wood, or wood that was completely replaced by silica.
silicate One of several rock-forming minerals that contain silicon, oxygen, and usually one or more other common elements.
silicates Group of minerals containing various amounts of the elements silicon and oxygen.
silicon oxygen tetrahedron A four-sided geometric form created by the tight bonding of four oxygen atoms to each other, and also to a single silicon atom that lies in the middle of the form.
silky luster Luster of minerals that have a very fine fibrous structure, causing it to display similar optical properties to silk cloth.
silt Accumulation of very small grains of rock, finer than sand.
simple oxides Compounds of metallic elements combined with oxygen. The simple oxides are a subgroup of the oxide group.
simple sulfides Group of sulfides that contain one or more true metals combined with sulfur.
sinkhole A circular, often funnel-shaped depression in the ground that forms when soluble rocks dissolve.
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.
skeletal Aggregate synonymous with dendritic. Some references note a difference in that skeletal is a single, tree-like entity, whereas dendritic is the same pattern implanted in rock.
slab Thick slice cut out of a solid mineral; a portion of the mineral.
slag Glassy substance formed as a by-product from the smelting of metallic ores.
slate A fine-grained, foliated metamorphic rock that develops from shale and tends to break into thin, flat sheets.
slide The mass movement of a single, intact mass of rock, soil, or unconsolidated material along a weak plane, such as a fault, fracture, or bedding plane. A slide may involve as little as a minor displacement of soil or as much as the displacement of an entire mountainside.
slip face The steep leeward slope of a dune.
slip plane A weak plane in a rock mass from which material is likely to break off in a slide.
slump 1. A downward and outward slide occurring along a concave slip plane. 2. The material that breaks off in such a slide.
smelt To melt ores for the extraction of a valuable metal they contain.
smooth fracture Synonym of even fracture
snowline The lowest point at which snow remains year-round.
soil The top layer of the earth's surface, which is composed of tiny rock particles mixed together with decaying organic matter.
soil horizon A layer of soil that can be distinguished from the surrounding soil by such features as chemical composition, color, and texture.
soil profile A vertical strip of soil stretching from the surface down to the bedrock and including all of the successive soil horizons.
solid solution A series formed when there are minerals in-between two isomorphous minerals. An example is the Plagioclase Feldspar group, which contains Albite and Anorthite as the anchor minerals, and minerals varying in amounts of those two minerals. Solid solutions may also be composed of minerals with a definite structure where one element may be minutely rep...
solidify Transforming from a liquid state to a solid state.
solifluction A form of creep in which soil flows downslope at a rate of 0.5 to 15 centimeters per year. Solifluction occurs in relatively cold regions when the brief warmth of summer thaws only the upper meter or two of regolith, which becomes waterlogged because the underlying ground remains frozen and therefore the water cannot drain down into it.
soluble Able to be dissolved. Solubility is the condition of being soluble.
sorosilicates Group of silicate minerals that are composed of groups of two tetrahedrons where one of the oxygen atoms is shared by both tetrahedrons; the other three oxygen atoms are not shared by another tetrahedron.
sorting The process by which a given transport medium separates out certain particles, as on the basis of size, shape, or density.
source rock A rock in which hydrocarbons originate.
spar Any non-metallic, lightly colored mineral with good cleavage.
specific gravity The ratio of the weight of a particular volume of a given substance to the weight of an equal volume of pure water.
specimen A mineral or rock of interest to collectors or scientists.
spectra Plural of spectrum.
spectral Having to do with the spectrum
spectrograph Device used to observe and record spectral changes.
spectrophotometer Device used to to measure the brightness of different portions of the spectrum.
spectroscope Device, such as a prism, which refracts white light and produces a spectrum which can be observed.
spectroscopy The science and study of the spectrum.
spectrum Composite of white light, which are the colors of the human eye can see. The spectrum is composed of the colors red, orange, yellow, green, blue, indigo, and violet in that order.
speleothem A mineral deposit of calcium carbonate that precipitates from solution in a cave.
sphenoidal Prism with wedge shaped corners, formed from a bipyramid that did not properly develop.
spheroidal weathering The process by which chemical weathering, especially by water, decomposes the angles and edges of a rock or boulder, leaving a rounded form from which concentric layers are then stripped away as the weathering continues.
spherulitic Aggregate consisting of rounded, ball like structures composed of radiating crystals. Spherulite is term ussed to describe any mineral composed of spherulitic aggregates.
spinel twin Form of contact twinning, in which two octahedral crystals that twin at the base, as depicted in the figure below. Named after the mineral Spinel, which most frequently exhibits this form of twinning.
spit A narrow, fingerlike ridge of sand that extends from land into open water.
splendent luster Synonym of metallic luster.
splintery splintery fracture Fracture forming elongated splinters. All fibrous minerals fall into this category.
stable Able to withstand normal environments without disintegrating.
stalactite An icicle-like mineral formation that hangs from the ceiling of a cave and is usually made up of travertine, which precipitates as water rich in dissolved limestone drips down from the cave's ceiling. See also stalagmite.
stalactitic Aggregate composed of long, icicle-like formations, like stalactites.
stalagmite A cone-shaped mineral deposit that forms on the floor of a cave and is usually made up of travertine, which precipitates as water rich in dissolved limestone drips down from the cave's ceiling. See also stalactite.
stalagmitic Shaped as a stalagmite, as a tall-domed structure. Many times confused with the term stalactitic, and many times substituted for that word.
star dune A dune with three or four arms radiating from its usually higher center so that it resembles a star in shape. Star dunes form when winds blow from three or four directions, or when the wind direction shifts frequently.
staurolite twin Form of penetration twinning where two monoclinic crystals form interpenetrating twins at 90�, forming a cross, as depicted in the figure below. Named after the mineral Staurolite, which most frequently exhibits this form of twinning. (Staurolite crystals may also twin at angles other than 90�, such as 60�.)
stellate Synonym of radiating.
stock Body of exposed igneous rock that intruded a layer of underground sedimentary rock, and is smaller than around 40 square miles (around 100 square kilometers).
stone Small piece of rock; may or may not refer to ornamental material.
strain The change in the shape or volume of a rock that results from stress.
stratification The behavior of having mineral sediments embedded in sedimentary rock.
stratovolcano A cone-shaped volcano built from alternating layers of pyroclastics and viscous andesitic lava. Stratovolcanos tend to be very large and steep.
stratum Layer of sedimentary rock compromised of one rock type. Layers of strata containing different rocks may form parallel bands of different rock. Strata is the plural form of stratum.
streak The color of a mineral in its powdered form. This color is usually determined by rubbing the mineral against an unglazed porcelain slab and observing the mark made by it on the slab.
streak plate Unglazed piece of porcelain, such as a tile, used to test a mineral's streak
stream A body of water found on the Earth's surface and confined to a narrow topographic depression, down which it flows and transports rock particles, sediment, and dissolved particles. Rivers, creeks, brooks, and runs are all streams.
stream discharge The volume of water to pass a given point on a stream bank per unit of time, usually expressed in cubic meters of water per second.
stream terrace A level plain lying above and running parallel to a stream bed. A stream terrace is formed when a stream's bed erodes to a substantially lower level, leaving its floodplain high above it.
stress The force acting on a rock or another solid to deform it, measured in kilograms per square centimeter or pounds per square inch.
striated Exhibiting tiny parallel lines or grooves.
