Geoscience Chapter 3 - Minerals

Mineral

A naturally occurring, inorganic solid with an orderly crystalline structure and definite but not fixed chemical composition.

Solid

A state of matter that can maintain its shape indefinitely.

Naturally Occurring

Created by natural processes rather than artificially in a laboratory.

Inorganic

Not an organic material; most minerals are not produced from living organisms.

Chemical Composition

The elements and proportions that make up a mineral, represented by a chemical formula.

Crystal Lattice

The specific, orderly arrangement of atoms in a mineral.

Crystalline Structure

The orderly internal arrangement of atoms in a mineral.

Glass

A solid with disordered atoms that lacks a crystalline structure.

Amorphous

Lacking an ordered crystalline structure.

Obsidian

A natural volcanic glass formed by extremely rapid cooling of lava.

Mineraloid

A natural material that resembles a mineral but does not meet all requirements for being a mineral.

Biogenic Mineral

A mineral created by living organisms.

Chemical Compound

A substance made of two or more elements joined together.

Native Mineral

A mineral made primarily of a single element, such as gold, sulfur, or copper.

Crystal

A single coherent mineral with geometric faces.

Grain

An irregularly shaped fragment of a larger crystal.

Rock

A naturally occurring solid aggregate of one or more minerals or mineral-like matter.

Polymineralic Rock

A rock composed of several different minerals.

Monomineralic Rock

A rock composed primarily of one mineral.

Euhedral Crystal

A well-formed crystal with sharp, recognizable crystal faces.

Anhedral Crystal

A crystal without well-formed external crystal faces.

Subhedral Crystal

A crystal with partially developed crystal faces.

Crystal Habit

The characteristic shape of individual mineral crystals.

Crystal Face

A flat external surface of a crystal.

Mineral Symmetry

The regular pattern of atomic arrangements expressed through mirror images or rotation.

Mineral Formation

The processes through which minerals form, including solidification from a melt and precipitation from a solution.

Precipitation

The formation of crystals from a solution when the solution becomes saturated.

Nucleation

The formation of initial seeds or sites around which crystals can grow.

Silicate Mineral

The most abundant group of minerals and major rock-forming minerals, based on silicon and oxygen.

Silicon-Oxygen Tetrahedron

The basic structural unit of silicate minerals consisting of silicon surrounded by oxygen atoms.

Isolated Tetrahedra Silicate

A silicate structure in which tetrahedra do not share oxygen atoms; examples include olivine and garnet.

Single-Chain Silicate

A silicate structure in which tetrahedra form single chains by sharing oxygen atoms; pyroxenes are examples.

Double-Chain Silicate

A silicate structure consisting of two linked chains of tetrahedra; amphiboles are examples.

Sheet Silicate

A silicate structure in which tetrahedra form sheets; micas and clay minerals are examples.

Framework Silicate

A silicate structure in which all oxygen atoms are shared between adjacent tetrahedra; quartz and feldspar are examples.

Felsic Silicate

A light-colored silicate mineral generally containing aluminum, potassium, calcium, and/or sodium.

Mafic Silicate

A dark silicate mineral containing significant iron and magnesium.

Feldspar

A common light-colored silicate mineral and important rock-forming mineral.

Quartz

A common framework silicate mineral made of a three-dimensional framework of silicon-oxygen tetrahedra.

Muscovite

A mica mineral with excellent cleavage in one direction and a Mohs hardness of 2.5.

Clay Minerals

Silicate minerals commonly produced by weathering of other silicates and common in soil.

Pyroxene

A common dark, mafic single-chain silicate mineral.

Amphibole

A common dark, mafic double-chain silicate mineral.

Olivine

A dark, iron- and magnesium-rich silicate mineral with isolated tetrahedra.

Biotite

A dark mica mineral containing iron and magnesium.

Garnet

A group of dark silicate minerals containing iron and magnesium.

Carbonate Mineral

A mineral containing the carbonate group; calcite is an example.

Calcite

A carbonate mineral with the formula CaCO3 that reacts with hydrochloric acid.

Dolomite

A carbonate mineral; it is not a silicate.

Gemstone

A mineral with special value because of rarity, beauty, or unusual characteristics.

Gem

A cut and polished stone created for jewelry.

Precious Gem

A particularly rare and expensive gemstone, such as diamond, ruby, sapphire, or emerald.

Semiprecious Gem

A less rare gemstone, such as topaz, aquamarine, or garnet.

Color

The part of visible light not absorbed by a mineral and therefore seen by our eyes.

Streak

The color of a mineral in powdered form.

Streak Plate

An unglazed porcelain tile used to determine a mineral's streak.

Luster

The way a mineral surface scatters light.

Metallic Luster

A luster that makes a mineral surface look like metal.

Nonmetallic Luster

A luster that does not look metallic and can include glassy, pearly, earthy, silky, or adamantine appearances.

Opaque

A mineral that does not transmit light.

Translucent

A mineral that transmits some light but not an image.

Transparent

A mineral that transmits both light and images.

Hardness

A mineral's resistance to scratching.

Mohs Scale

A hardness scale ranging from 1 to 10.

Cleavage

The tendency of a mineral to break along planes of weaker atomic bonds in its crystal lattice.

Fracture

The tendency of a mineral to break in ways that are not along cleavage planes.

Density

Mass per unit volume, calculated as d = m/v.

Specific Gravity

The ratio of a mineral's weight to the weight of an equal volume of water.

Tenacity

A mineral's resistance to breaking or deforming.

Brittle

The tendency to shatter when struck.

Malleable

The ability to deform into shapes or thin sheets.

Sectile

The ability to be cut into thin shavings.

Elastic

The ability to return to the original shape after being bent.

Effervescence

Fizzing caused by a mineral reacting with acid and releasing carbon dioxide.

Magnetic Property

The ability of certain iron-rich minerals to be attracted to a magnet.

Optical Properties

Mineral properties involving light, including color, streak, luster, and light transmission.

Strength Properties

Mineral properties related to resistance to breaking or deforming, including hardness, tenacity, cleavage, and fracture.

Weight/Mass Properties

Mineral properties involving mass and weight, especially density and specific gravity.