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Inland Lapidary - Gem glossary
Category: General technical and industrial > Gems and Geology
Date & country: 27/10/2013, USA
Words: 1119


enaniotropic
Describing a mineral that does not have a consistent crystal structure, meaning that it can transform back and forth into its paramorph when conditions are suitable. Monotropic minerals cannot transform back and forth into their paramorphs. Once they change, they cannot change back without the crystal structure being destroyed.

encrust
To form a coating over.

encrustation
A crusty coating.

energy level
The path of a given electron's orbit around a nucleus, marked by a constant distance from the nucleus.

engrave
To carve letters or an image out of a gemstone.

environment
Area or region conducive for the development of a mineral. Certain minerals only develop in certain environments.

epicenter
The point on the Earth's surface that is located directly above the focus of an earthquake.

epitaxy
The growth of a crystal of one mineral on or around a crystal of another mineral.

epithermal vein
Vein formed at shallow depths from unstable hot solutions.

epsom salts
Salt made of magnesium sulfate (MgSO4 �7H2O) used for stomach medications. Epsom salt is extracted from the mineral Epsomite.

equant
Synonym of equidimensional

equidimensional
Equal in length, width, height, and angles.

equilibrium line
The point in a glacier where overall gain in volume equals overall loss, so that the net volume remains stable. The equilibrium line marks the border between the zone of accumulation and the zone of ablation.

eroded
Having gone through the process of erosion.

erosion
The process by which particles of rock and soil are loosened, as by weathering, and then transported elsewhere, as by wind, water, ice, or gravity.

esker
A ridge of sediment that forms under a glacier's zone of ablation, made up of sand and gravel deposited by meltwater. An esker may be less than 100 meters or more than 500 kilometers long, and may be anywhere from 3 to over 300 meters high.

evaporate
Going through the process of evaporation.

evaporation
The process in which water and moisture rises up to the air and forms vapor.

evaporite
An inorganic chemical sediment that precipitates when the salty water in which it had dissolved evaporates.

even fracture
Mineral fracture forming a smooth, flat surface.

extract
To separate a valuable constituent from its ore.

extraterrestrial
Originating off of the earth. Meteorites are extraterrestrial.

face
1) An individual flat section of a faceted gem. 2) Crystal face.

facet
A desired surface displayed in a gem. It may grow naturally but is usually hand cut. This definition includes the meaning of a specific cuts for gems.

faceting
Cutting from a rough stone into a gem, creating a facet

fall
The fastest form of mass movement, occurring when rock or sediment breaks off from a steep or vertical slope and descends at a rate of 9.8 meters per second. A fall can be extremely dangerous.

fault
A fracture dividing a rock into two sections that have visibly moved relative to each other.

fault block
A section of rock separated from other rock by one or more faults.

fault-block mountain
A mountain containing tall horsts interspersed with much lower grabens and bounded on at least one side by a high-angle normal fault.

fault-zone metamorphism
The metamorphism that acts on rocks grinding past one another along a fault and is caused by directed pressure and frictional heat.

feldspar (group)
Group of minerals that are aluminum silicates containing potassium, sodium, and/or calcium. Some minerals in this group are wrongly classified as other minerals in this group. This is the most abundant group of minerals on the earth, and the building block of many rocks. The feldspar group is in the tectosilicates subdivision of the silicates group...

feldspathoid (group)
Group of minerals that are very similar to the feldspars. The difference is that the feldspathoids lacked the amount of silica to fully make them into feldspars when they were formed. They, as feldspars, are aluminum silicates of potassium, sodium, and/or calcium. The feldspathoid group is in the tectosilicates subdivision of the silicates group.

felsic
Consisting mostly of silica (more than 65 percent), in the form of quartz and feldspar. Can also be applied in reference only to the feldspars.

ferromagnetic
Greatly attracted to magnetic fields. Ferromagnetism is the magnetic property in certain materials that causes them to be attracted to magnetic fields.

ferrous
Containing iron.

ferruginous
1) Containing iron. 2) Appearing like iron. 3) Having a dull reddish-brown color similar to rust.

fiber
Individual segment or crystal of a fibrous aggregate.

fibrous
Aggregate describing a mineral constructed of fine, usually parallel threads. Some fibrous minerals contain cloth-like flexibility, meaning they can be bent around and feel like cotton.

filiform
Aggregate composed of thin, intergrown, twisted, pipelike strands. (i.e. flos-ferri)

firn
Firmly packed snow that has survived a summer melting season. Firn has a density of about 0.4 gram per cubic centimeter. Ultimately, firn turns into glacial ice.

fishtail twin
Form of repeated twinning in which two monoclinic crystals join as on the side, one reflecting the other, forming a fishtail or flower-like model. See also swallowtail twin.

fissile
Easily split along parallel layers.

fissility
The property exhibited on fissile rocks or minerals that is responsible for the splitting along parallel layers. Fissility exhibited on minerals is either cleavage or parting.

fission tracks
Marks left in the latticework of a mineral crystal by subatomic particles released during the fission of a radioactive atom trapped inside the crystal.

fjord
A deep, steep-walled, U-shaped valley formed by erosion by a glacier and submerged with seawater.

flakey
Aggregate containing small, flat, almost bendable flakes.

flame test
Complex, scientific test which is conducted to identify a mineral. A small fragment of a mineral is placed on the end of a platinum wire and held in a flame. Different metals present in the mineral change the color of the flame (such as sodium, yellow ; copper, blue and green ; potassium, violet).

flaw
Inclusion or crack in a gemstone that usually demotes its value.

flexible / flexibility
Minerals that are capable of being bent without breaking are said to be flexible. If a flexible mineral will return to its original position after stress is released, it is said to be flexible and elastic. If it does not return to its original position, but retains the position it was given after being bent, it is said to be flexible but inelastic....

floating crystal
Crystal that developed without being attached to rock, such as being grown artificially in a lab or having been grown naturally in clay or water. All the sides of floating crystals are intact.

flood tide
A tide that raises the water surface of an ocean and moves the shoreline farther inland.

floodplain
The flat land that surrounds a stream and becomes submerged when the stream overflows its banks.

flow
A relatively rapid mass-movement process that involves a mixture of rock, soil, vegetation, and water moving downslope as a viscous fluid. Within a flow (such as a mudflow), each particle, regardless of its size, moves independently.

flow banding
Layered grouping of different rocks formed from the flowing of lava.

flowstone
Calcium carbonate formed by mineral-rich water that deposits the dissolved mineral on the walls of caverns and cliffs, forming a smooth and humpy growth. As long as there is water flowing down, the layer of flowstone accumulates.

fluorescence
Emission of visible light by a substance, such as a mineral, that is currently exposed to ultraviolet light and absorbs radiation from it. The light appears in the form of glowing, distinctive colors. The emission ends when the exposure to ultraviolet light ends. Minerals describes as fluorescent have the ability to fluoresce.

fluorescent lamp
Lamp that gives off ultraviolet light while blocking out white light, which causes fluorescent minerals to react.

fluvial
Said of eroded material that gets transported by rivers or streams. Synonym of alluvial.

flux
Any liquid added to another liquid to improve flow, usually to prevent the formation of oxides.

foci
The precise point within the Earth's crust or mantle where rocks begin to rupture or move in an earthquake.

fold
A bend that develops in an initially horizontal layer of rock, usually caused by plastic deformation. Folds occur most frequently in sedimentary rocks.

foliation
The arrangement of a set of minerals in parallel, sheet-like layers that lie perpendicular to the flattened plane of a rock. Occurs in metamorphic rocks on which directed pressure has been exerted.

forearc basin
A depression in the sea floor located between an accretionary wedge and a volcanic arc in a subduction zone, and lined with trapped sediment. See also backarc basin.

foreshock
A minor, barely detectable earthquake, generally preceding a full-scale earthquake with approximately the same focus. Major quakes may follow a cluster of foreshocks by as little as a few seconds or as much as several weeks.

foreshore
The portion of a beach that lies nearest to the sea, extending from the low-tide line to the high-tide line.

form
The setting of all the crystal faces and the structure of a mineral.

fossil
Animal or plant remains of a previous age embedded and preserved in rock. Rocks containing fossils are described as fossiliferous.

fossil fuel
A nonrenewable energy source, such as oil, gas, or coal, that derives from the organic remains of past life. Fossil fuels consist primarily of hydrocarbons.

fossilization
The process of an organic substance being transformed into a fossil.

fossilize
To form into a fossil.

fossilized
Having been transformed into a fossil.

fourling
Twinned intergrowth of four individual crystals

fractional crystallization
The process by which a magma produces crystals that then separate from the original magma, so that the chemical composition of the magma changes with each generation of crystals, producing igneous rocks of different compositions. The silica content of the magma becomes proportionately higher after each crystallization.

fracture
1. (n) A crack or break in a rock. 2. (v) To break in random places instead of cleaving. 3. The characteristic way a mineral breaks when put under stress, aside from cleavage. Said of minerals.

framework silicates
Synonym of tectosilicates.

freezing point
The temperature it takes a substance to transform from liquid to solid. Every substance has a different freezing point.

friable
Describes a mineral which easily crumbles. Minerals with an earthy fracture are friable.

fringing reef
A reef that forms against or near an island or continental coast and grows seaward, sloping sharply toward the sea floor. Fringing reefs usually range from 0.5 to 1.0 or more kilometers in width.

frost wedging
A form of mechanical weathering caused by the freezing of water that has entered a pore or crack in a rock. The water expands as it freezes, widening the cracks or pores and often loosening or dislodging rock fragments. As the ice forms, it attracts more water, increasing the effects of frost wedging.

fumarole
Volcanic vent where smoke and gases escape from.

gabbro
Any of a group of dark, dense, phaneritic, intrusive rocks that are the plutonic equivalent to basalt.

gamma rays
Form of electromagnetic radiation which contains the shortest wavelength of the spectrum. Gamma rays easily penetrate matter because of their short wavelength.

gangue material
Worthless material in which valuable metals or gems occur.

garnet paper
Sandpaper composed of tiny, hard, Garnet crystals, glued on to it for use as an abrasive.

geiger counter
Instrument that measures intensity of radiation. It is very useful for detecting radioactive minerals.

gem
A cut mineral or pearl refined for use as an ornament.

gemology
The science and procedures involved in mining, faceting, and marketing of gemstones. A person studying in this discipline is a gemologist.

gemstone
Any mineral or naturally occurring substance in an raw, uncut state that is capable of being a gem.

geochronology
The study of the relationship between the history of the Earth and time.

geode
Hollow rock that is filled or partially filled with crystals.

geologic
Having to do with geology.

geologic time scale
The division of all of Earth history into blocks of time distinguished by geologic and evolutionary events, ordered sequentially and arranged into eons made up of eras, which are in turn made up of periods, which are in turn made up of epochs.

geology
The scientific study of the Earth, its origins and evolution, the materials that make it up, and the processes that act on it.

geophysics
The branch of geology that studies the physics of the Earth, using the physical principles underlying such phenomena as seismic waves, heat flow, gravity, and magnetism to investigate planetary properties.

geyser
A natural spring marked by the intermittent escape of hot water and steam.

glacial abrasion
The process by which a glacier erodes the underlying bedrock through contact between the bedrock and rock fragments embedded in the base of the glacier. See also glacial quarrying.

glacial drift
A load of rock material transported and deposited by a glacier. Glacial drift is usually deposited when the glacier begins to melt.

glacial erratic
A rock or rock fragment transported by a glacier and deposited on bedrock of different composition. Glacial erratics range from a few millimeters to several yards in diameter.

glacial quarrying
The process by which a glacier erodes the underlying bedrock by loosening and ultimately detaching blocks of rock from the bedrock and attaching them instead to the glacier, which then bears the rock fragments away. See also glacial abrasion.

glacial till
Drift that is deposited directly from glacial ice and therefore not sorted. Also called till. See also glacial drift.