Welcome to the Mineral and precious stone glossary

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z  All terms

Having crystals large enough to be seen with an unaided eye.

Describing dark colored rocks or minerals that are composed particularly of magnesium and iron.

Molten rock under the crust of the earth.

Igneous.

Term describing any igneous rock.

1) Industrial material made of magnesium oxide.
2) Describing a mineral that is composed of magnesium oxide.

An object that is surrounded by a magnetic field, causing iron or steel materials to be attracted to it. (See magnetism for more information.)

This term can be used to describe materials that give off magnetic fields (i.e. act as a magnet), or materials that are attracted to magnetic fields. To note the distinction, this guide defines "magnetic" as giving off a magnetic field, and "attracted to magnets" as being attracted to a magnetic field.

Area encompassing a magnet or electric current which has the ability to attract or repel certain objects anywhere in the field. Points in the magnetic field closer to the magnet or electrical current are stronger, and points further away are weaker.

The phenomenon of certain metals to attract other metals. (See Magnetic for more information.)

Tenacity of a certain minerals that are able to be pounded into thin sheets.

Aggregate describing smooth, rounded, agglomerations. Rounded agglomerations of mammilary aggregates are larger than reniform agglomerations and considerably larger than botryoidal agglomerations.

The middle layer of the earth -- between the crust and the core.

Term used to describe a rock or mineral that has no particular shape, either because

1. it is non-crystalline
2. it is composed of tiny, unorganized crystals
3. it is a shapeless fragment of a crystal

A material that has an embedded crystal inside or emerging from it.

The temperature it takes a certain material to change from a solid to liquid state.

Vein created due to intense heat (in range from around 390° to 570° F [200° to 300° C] ).

Any of a category of electropositive (positively charged) elements or combinations of them in the form of minerals that exhibit a metallic luster, malleability, ductility, and conductivity.

Having the attributes of a metal. Sometimes can be used to describe a mineral with a metallic luster even though it is not a true metal.

Exhibiting the luster of a metal, which is opaque and reflective. Some minerals exhibit a metallic luster even though they are not true metals.

The metallic elements are minerals belonging to the native elements group. They consist of minerals that are pure elements or metallic alloys. They are all true metals, that is they have a metallic luster, are malleable and ductile, and are good conductors of electricity.

The science and procedures involved in extracting metals from ore, refining the metals, blending them into alloys, and fashioning useful objects from them. Three forms of metallurgy are hydrometallurgy, electrometallurgy, and pyrometallurgy.

Crystalline minerals that lose their crystal structure due to radioactive destruction.

The process which a metamict mineral goes through.

Mineral environment where the minerals are secondary in origin, forming from alteration through heat and pressure. See also metamorphic rock.

Secondary rock that formed from an original rock, through heat or pressure.

This term either refers to the metasilicate chains (inosilicates), the metasilicate rings (cyclosilicates), are both the metasilicate chains and rings.

The chemical alteration of rocks or minerals by interaction with liquids. The alteration must only take place if the rock or mineral was not in a molten state in order for it to be metasomatism.

The act of being metastable.

Describing the condition of radioactive minerals which cannot withstand their composition and begin to decay. Also refers to minerals that crystallize at a certain temperature and can only retain the initial crystal structure at certain temperatures. Synonym of unstable

Mass of extraterrestrial rock that gets pulled in to the earth's gravitational pull. Some meteors can be seen streaking across the atmosphere before they burn up or land on earth. These are known as "shooting stars". Meteors that don't burn up and land on the earth are known as meteorites.

Solid mass suspended in outer space that revolves around the sun. Meteoroids are smaller than asteroids. See also meteor.

Term used to describe the extraterrestrial nature of meteors and meteorites.

Meteor that did not fully burn up in the atmosphere and landed on the earth. (See Iron/Iron-Nickel for more information)

Individual member of the mica group. May also refer to any mineral with perfect basal cleavage that can be "peeled".

Group of related minerals that contain aluminum silicate. The percentage of its component elements may vary, which causes many people not to recognize the micas as a series. The micas are soft and have perfect basal cleavage, and can be seen when a mica is "peeled". The mica group is in the phyllosilicates subdivision of the silicates group.

Aggregate of compact, flat, parallel, flexible, and peelable sheets, or describing minerals that occur in such aggregates.

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. (See organizing a collection for more information about micromounts.)

Deposit in which minerals or ore is or was industrially extracted. (See Finding minerals for more information about mines.)

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. See What is a Rock and What is a Mineral for more information.

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. See also series.

Amorphous, inorganic substance lacking a crystal structure. They are mineral in nature but lack a crystal structure, and thus cannot scientifically be classified as minerals. Many references, though, still classify them as minerals. Two important mineraloids are Opal and Obsidian.

The study of minerals.

Individual practicing in the subject of mineralogy.

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

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 partialy replacing the iron. See also solid solution.

A measurement that was devised by Austrian scientist Fredrick Mohs to determine the hardness of a mineral. (See Hardness in mineral properties for more information.)

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.

The arrangement of molecules in a substance.

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

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.

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

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.

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

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°. (See Crystals in mineral properties for more information) Animated figure of monoclinic crystal system

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.

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

The rock a mineral or minerals is found implanted in.

Spotted or speckled with different tints or colors.

Exhibiting two or more colors on a single specimen.

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

Rock fragments separated from their original rock from shifting of plates in the fault zones.