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

Composed of tiny crystals that cannot be seen with an unaided eye. Microcrystalline minerals appear amorphous, since no apparent crystal shape can be detected.

A mineral specimen that is not more 1/10 of an inch (15 -27 mm.) in size.

A rock that incorporates both metamorphic and igneous materials.

1) Deposit in which minerals or ore is or was industrially extracted. 2) To exploit a mineral deposit.

Individual who exploits mineral deposits.

Any naturally occurring, three dimensional, inorganic substance, with a chemical structure that can be exact, or can vary within limits. Elements that occur naturally are also listed as minerals.

mineral group
A scientifically recognized selection of minerals similar in structure. All groups have a specific group name, and individual minerals may also be categorized. A mineral in the group may have the same name as group name. An example is the Olivine Group, which contains the minerals Forsterite, Olivine (also known as Chrysolite), and Fayalite.



A naturally occurring, usually inorganic, solid consisting of either a single element or a compound, and having a definite chemical composition but lacking a systemic internal arrangement of atoms. Opal and Obsidian are two examples.

The process of extracting minerals or metal ore out of a mine or mineral deposit.

mixed crystal
Crystal containing an indefinite amount of two or more elements or a slight amount of one element replacing another. An example is Siderite, which is iron carbonate (FeCO3), but commonly contains small amounts of other elements, such as zinc and manganese partially replacing the iron.

The seismic discontinuity between the base of the Earth's crust and the top of the mantle. P waves passing through the Moho change their velocity by approximately one kilometer per second, with the higher velocity occurring in the mantle and the lower in the crust.

Mohs hardness scale
A measurement that was devised by Austrian scientist Fredrick Mohs to determine the hardness of a mineral.

Having to do with molecules.

molecular arrangement
The arrangement of molecules in a substance.

molecular structure
The quantity and method of arrangement concerning the molecules in a particular substance.

The fundamental structure in all minerals. Molecules are chemically grouped atoms that are the smallest particles a mineral can be divided without changing its chemical or physical properties. A chemical grouping of one element is also considered a molecule.

Family of marine creatures, which includes the oyster and snail, which have a soft fleshy body surrounded by a calcareous shell.

Hot liquid that results from the melting of solid material at great temperatures.

molten rock
Liquid rock at extremely high temperatures under the surface of the earth. When molten rock cools down it solidifies and forms rocks and minerals.

Group of minerals composed with the molybdate radical (MoO4) and a metallic element. These minerals are heavy, soft, and brittle. The molybdates are usually categorized with the chemically related tungstates, in which they can be partially replaced by.

Moment-magnitude scale
A recently developed alternative to the Richter scale used to measure more accurately the amount of energy released by large earthquakes. This scale involves measurement of an earthquake's seismic moment.

Exhibiting only a single color. Minerals that are monochromatic occur in only one color, no matter what specimen.

monoclinic (crystal system)
Any mineral that falls under the following specifications belongs to the monoclinic crystal system: Three axes, all of them are unequal in length. Two of them are at right angles to each other, while the third is lies at an angle other than 90�.

Mineral that permanently changes over into its paramorph, meaning that once it transforms under suitable conditions it cannot change back to the original mineral without the crystal structure being destroyed. Enaniotropic minerals can change back and forth when conditions are suitable.

A single, large mass of glacial till that accumulates, typically at the edge of a glacier.

mother rock
The rock a mineral or minerals is found implanted in.

1) The iridescent inside of a mollusk shell, which is used as an ornament. Not to be confused with pearl. 2) Exhibiting a luster similar to the inside of a mollusk shell or shirt button. Many mica's exhibit a pearly luster, and some minerals with a pearly luster have an iridescent hue. Some minerals may exhibit a pearly luster on cleavage cracks pa...

Spotted or speckled with different tints or colors.

A fracture that develops at the top of a layer of fine grained, muddy sediment when it is exposed to the air, dries out, and then shrinks.

A detrital sedimentary rock composed of clay-sized particles.

Exhibiting two or more colors on a single specimen.

multiple oxides (subgroup)
Minerals that are compounds of two different metallic elements combined with oxygen. The multiple oxides are a subgroup of the oxides.

The iridescent inside of a mollusk shell, which is used as an ornament. Not to be confused with pearl.

Composed of only a single element; not combined with any other elements.

native elements group
Group of minerals containing naturally occurring minerals with a molecular structure of only one element; examples are Copper, Sulfur, and Diamond. Also included in this group are metallic and semi-metallic alloys, which are minerals composed only of two or more metallic or semi-metallic elements of varying percentage; two examples are Iron-Nickel ...

natural bridge
An arch-shaped stretch of bedrock remaining in a karst region when the surrounding bedrock has dissolved.

natural glass
Igneous rocks that forms when rapid cooling of molten rock occurs. Natural glasses, such as Obsidian, are amorphous with a rounded shape, and usually contain conchoidal fractures.

natural spring
A place where groundwater flows to the surface and issues freely from the ground.

Group of silicate minerals that contain only single, non-combining groups of tetrahedrons.

A particle that is found in the nucleus of an atom, has a mass approximately equal to that of a proton, and has no electric charge.

nitrates group
Group of minerals that contain one or more metallic elements plus the nitrate radical (NO3). These minerals are all fragile and soft. With one exception, they are all soluble in water, and are therefore found only in arid regions, primarily in dry lake deposits. The nitrates are a small group, and are sometimes classified as a sub-category of the c...

nitric acid
(HNO3) Corrosive acid used in the manufacture of explosives and fertilizers. It is a very destructive liquid and will destroy many minerals.

Spherical, in the shape of a small rounded lump.

Aggregate consisting of a spherical lump, usually from groups of small crystals.

Not containing any crystals; amorphous mineral or variety of mineral.

non-metallic elements
The nonmetallic elements are minerals that belong in the native elements group and don't exhibit any metallic properties (except for Graphite, which has a metallic luster). They are light in weight and can be transparent.

not crumbling to a powder when crushed.

Substance that does not exhibit the properties of a true metal.

normal fault
A dip-slip fault marked by a generally steep dip along which the hanging wall has moved downward relative to the footwall.

nu�e ardente
A sometimes glowing cloud of gas and pyroclastics erupted from a volcano and moving swiftly down its slopes. Also called a pyroclastic flow.

nuclear fission
The division of the nuclei of isotopes of certain heavy elements, such as uranium and plutonium, effected by bombardment with neutrons. Nuclear fission causes the release of energy, additional neutrons, and an enormous quantity of heat. Nuclear fission is used in nuclear power plants and nuclear weapons. A by product of nuclear fission is toxic rad...

nuclear fusion
The combination of the nuclei of certain extremely light elements, especially hydrogen, effected by the application of high temperature and pressure. Nuclear fusion causes the release of an enormous amount of heat energy, comparable to that released by nuclear fission. The principal by product of nuclear fusion is helium.

The central part of an atom, containing most of the atom's mass and having a positive charge due to the presence of protons.


Compact, waterworn, amorphous mass, found in placer deposits.

oblique slip
Fault motion that involves both dip-slip and strike-slip movement of fault blocks.

The area where a particular mineral is found.

ocean trench
A deep, linear, relatively narrow depression in the sea floor, formed by the subduction of oceanic plates.

Amorphous, yellow to red substance composed of iron compounds such as Hematite and Limonite.

Three dimensional polyhedron that is a combination of a cube and octahedron.


Eight sided polyhedron; all sides are equidimensional and bisect at at the same angle. Minerals shaped as octahedrons belong to the isometric system.

A scientific law stating that all atoms, except those of hydrogen and helium, require eight electrons in the outermost energy level to maintain chemical stability.

oil of vitriol
Synonym of sulfuric acid.

oil sand
A mixture of unconsolidated sand and clay that contains a semi-solid bitumen.

oil shale
A brown or black clastic source rock containing kerogen.

oily luster
Synonym of greasy luster: Luster of a mineral that appears coated with grease. Some minerals are coated with chemicals to induce a greasy luster.

Aggregate composed of very small, spherical particles.

Effect seen in a few minerals, chiefly opal (hence its name) which cause it to exhibit a glimmer of different colors when rotated or seen in different angles. Opalescent describes mineral exhibiting this effect.

The common habit of Opal that it replaces material, such as wood, shells, and other minerals.

To be chemically altered to Opal.

Not able to transmit light, which in effect disables it from letting an object be seen through it.

ophiolite suite
The group of sediments, sedimentary rocks, and mafic and ultramafic igneous rocks that make up the oceanic lithosphere.


Branch of physics that deals with light and the electromagnetic radiation; certain areas are dispersion, absorption spectra, reflection, and refraction.

Composed of carbon compounds; being from the source of living organisms.

Mountain formation, as caused by volcanism, subduction, plate divergence, folding, or the movement of fault blocks. Also called orogeny.

orthorhombic crystal system
Any mineral that falls under the following specifications belongs to the orthorhombic crystal system: Three axes, all are unequal in length. All three axes are at 90� to each other.

Synonym of nesosilicates: Group of silicate minerals that contain only single, non-combining groups of tetrahedrons.

oscillatory motion
The circular movement of water up and down, with little or no change in position, as a wave passes.

Bedrock revealed at the surface of the earth.

A load of sediment, consisting of sand and gravel, that is deposited by meltwater in front of a glacier.

oxbow lake
A crescent-shaped body of standing water formed from a single loop that was cut off from a meandering stream, typically by a flood that allowed the stream to flow through its floodplain and bypass the loop.

The process of combining with oxygen ions. A mineral that is exposed to air may undergo oxidation as a form of chemical weathering.

oxidation minerals
Minerals that form after being altered from being exposed in the oxidation zone.

oxidation zone or oxidized zone
Area of a deposit where the rock is exposed to air and therefore is affected by wind, rain, pressure, and air, which chemically affects the minerals embedded in the rock and alters them to secondary minerals.

Group of minerals that are compounds of one or more metallic elements combined with oxygen, water, or hydroxyl (OH). The oxide group contains the greatest variations of physical properties. Some are hard, some soft. Some have a metallic luster, others are clear and transparent. The Oxide group is divided into the Simple Oxides, Hydroxides, Multiple...

Property exhibited in certain minerals that cause them to tarnish, or discolor upon contact with air. Also term used to describe the chemical alteration of one mineral into another mineral through oxidation.

P-wave shadow zone
The region that extends from 103� to 143� from the epicenter of an earthquake and is marked by the absence of P waves. The P-wave shadow zone is due to the refraction of seismic waves in the liquid outer core. See also S-wave shadow zone.

1. The fixed orientation of a rock's crystals, based on the Earth's magnetic field at the time of the rock's formation, that remains constant even when the magnetic field changes. 2. The study of such phenomena as indicators of the Earth's magnetic history.

Individual practicing in the subject of paleontology.

The science and study of previous life forms, primarily in the form of fossils.

An ancient, buried soil whose composition may reflect a climate significantly different from the climate now prevalent in the area where the soil is found.

Paleozoic Era
The earliest era of the Phanerozoic Eon, marked by the presence of marine invertebrates, fish, amphibians, insects, and land plants.

parabolic dune
A horseshoe-shaped dune having a concave windward slope and a convex leeward slope. Parabolic dunes tend to form along sandy ocean and lake shores. They may also develop from transverse dunes through deflation.

The crystallization mode of one mineral in retrospect to other minerals. Paragenesis is applied to determine the conditions and qualifying factors necessary for a mineral to form.

Weakly attracted to magnetic fields.

Magnetic property in certain iron bearing minerals that cause them to be weakly attracted to magnetic fields.