Amateur Geologist Structured Geological Glossary: Minerals

Structured Geological Glossary: Minerals

x-ray diffraction	In mineralogy, the process of identifying mineral structure by exposing crystal to X-rays and studying the resulting diffraction pattern.
unit cell	The smallest contiguous group of atomic structural units in a mineral that can be repeated in three directions to form a crystal.
interfacial angle	The angle between two crystal faces of a crystal, characteristic of a mineral's symmetry.
octahedral coordination	The packing of six ion around an ion of opposite charge to form an octa-hedron.
index of refraction	" The ratio of the speed of light in a vacuum to the speed in a material; this ratio determines the amount that light is refracted as it passes into a crystal. "
mineral	A naturally occurring element or compound with a precise chemical formula and a regular internal lattice structure. Organic products are usually not included.
most abundant elements	Element Percentage O 46.6 Mg 2.09 Si 27.62 Ti .044 Al 8.13 H 0.14 Fe 5.00 Mn 0.1 Ca 3.63 Mn 0.1 Na 2.83 S 0.05 K 2.59 C 0.03
mineralogy	The study of mineral composition, structure, appearance, stability, occurrence, and associations.
Mohs scale of hardness	An empirical, ascending scale of mineral hardness with talc as 1, gypsum 2, calcite 3, fluorite 4, apatite 5, orthoclase 6, quartz 7, topaz 8, corundum 9, and diamond 10.
hardness	A measure of a mineral's resistance to scratching. The hardness of a mineral is measured by scratching it against another substance of known hardness.
cleavage	The tendency of a mineral to break along weak planes.
crystallization	Growth of mineral (crystalline solid) from a liquid or gas
streak	" The fine deposit of mineral dust left on an abrasive surface when a mineral is scraped across it; especially the characteristic color of the dust. "
streak plate	A ceramic abrasive surface for streak tests.
dendritic crystals	Crystals that grow in a branching form resembling trees.
massive rock	A rock that is little or not at all broken by joint, cracks, foliation, or bedding, tending to present a homogeneous appearance.
zoned crystal	A single crystal of one mineral that has a different chemical composition in its inner and outer parts. Formed from minerals belonging to a solid-solution series, and caused by the changing concentration of elements in a cooling magma that results from crystals settling out.
fluid inclusion	Bubble of liquid or gas trapped inside a solid mineral-phase, usually formed during crystallization of the mineral in the presence of a fluid phase. Tiny cavities, 1.0-100 microns in diameter, containing liquid and/or gas, formed by the entrapment of fluid in crystal irregularities. Fluid inclusion provide information on the temperature, pressure, and chemical composition of the fluids and/or gases trapped at the time of mineral formation.
opaque	A mineral which transmits no light through a thin section under a microscope. Usually a native metal, sulfide, or metallic oxide mineral.
isotropic substance	One in which the magnitude of a physical property, such as transmission of light is independent of crystallographic direction.
extinction angle	The angle between a crystallographic direction, such as a face or cleavage plane, and the direction in which all light is blocked by a pair of crossed polarizers.
luster	The general textural impression of a mineral surface, given by the light reflected from it. Terms such as metallic, submetallic are standardized but subjective.
vitreous	Similar to broken glass.
carbonization	The mode of fossilization in which liquid and gases escape, leaving a residue of carbon on the surface of an impression of the organism.
native metal	A natural deposit of a metallic element in pure metallic form, neither oxidized nor combined with sulfur or other elements.
massive sulfide ore deposit	Occurrence of a concentrated mass of sulfide mineral such as pyrite, sphalerite or chalcopyrite in one place, as opposed to their being disseminated or occurring in vein.
limonite	A mineral composed of iron oxides and water. Rust. Very common in many rocks after weathering at the Earth’s surface. Imparts brown or yellow color to many rocks.
magnetite	Iron oxide mineral (Fe3O4). Usually tiny black, metallic crystal. Magnetite will attract a magnet and sometimes, in a rock, a hiker’s compass needle.
pyrite	Iron sulfide mineral (FeS). Forms silvery to brassy metallic cubes or masses. Common in many rocks. Known as fool’s gold. Weathered pyrite produces limonite (iron oxide) that stains rock brown. or yellow.
calcite	Mineral made of calcium carbonate (CaCO3). Generally white, easily scratched with knife. Most seashells are made of calcite or related mineral. This is the lime of limestone.
carbonate mineral	A mineral in which the basic building block is a carbon atom linked to three oxygen atoms. Calcite, aragonite and dolomite are the most abundant examples found in sediment and sedimentary rocks.
carbonate ion	The anion group CO3 with a charge of minus two.
dolomite	A magnesium-rich carbonate sedimentary rock. Also, a magnesium-rich carbonate mineral (CaMgCO3)
anhydrite	The mineral that consists of calcium sulfate (CaS04) or the rock composed of this mineral.
fluorescence	Emission of a certain wavelength light resulting from and occurring only during the absorption of light of another wavelength.
halite	Halite (NaCl) is a mineral and is known commonly as salt - the same salt that we sprinkle on our food. Like gypsum, it is an evaporite mineral that form from seawater
quartz	One of the most common mineral in the Earth’s crust (and in some new-age boutiques). Made up of silicon dioxide (SiO2),lso called silica. Commonly in white masses. Crystals are clear, glassy 6-sided prisms.
mica	"Group of silicate mineral composed of varying amounts of aluminum, potassium, magnesium, iron and water. All mica form flat, plate-like crystal. Crystals cleave into smooth flakes. Biotite is dark, black or brown mica; muscovite is light-colored or clear mica"
muscovite	One of the mica family of mineral. Muscovite is light-colored or clear mica, sometimes called isingglass.
biotite	A common rock-forming mineral of the mica family. Biotite is a black or dark brown silicate rich in iron, magnesium, potassium, aluminum, and, of course, silica. Like other micas, it forms flat book-like crystal that peal apart into individual sheets on cleavage planes.
phlogopite	A magnesium-rich member of the mica mineral family. Phlogopite is a yellowish-brown to coppery-colored mica. Like all micas, phlogopite form flat, plate-like crystal that cleave into smooth flakes.
ferro-magnesian elements	Elements that are readily substituted into silicate mineral that have Fe and Mg as major constituents. Examples include Cr, Ni, V, Sc, Co.
feldspar	Family of silicate mineral containing varying amounts of potassium, sodium and calcium along with aluminum, silicon and oxygen. Potassium feldspar contain considerable potassium. Plagioclase feldspars contain considerable sodium and calcium. Feldspar crystal are stubby prisms, generally white, gray, or pink.
sanidine	A type of potassium feldspar that form only at high temperature. Common in potassium-rich volcanic rock.
plagioclase feldspar	A member of the feldspar mineral family. Plagioclase feldspars are silicate that contain considerable sodium and calcium. Feldspar crystal are stubby prisms, generally white to gray and a glassy luster.
pyroxene	Family of silicate mineral containing iron, magnesium, and calcium in varying amounts. Differ from amphibole family by lack of water in the crystal. The most common variety, augite, contains aluminum as well. Generally form very dark green to black stubby prisms.
amphibole	" A family of silicate mineral forming prism or needlelike crystal. Amphibole minerals generally contain iron, magnesium, calcium and aluminum in varying amounts, along with water. Hornblende always has aluminum and is a most common dark green to black variety of amphibole; it, forms forming in many igneous and metamorphic rocks. Actinolite has no aluminum; it and is needle-shaped and light green. Blue amphibole contains sodium and, of course, is bluish in color. "
hornblende	See amphibole.
actinolite	A bright to gray-green member of the amphibole mineral family. In addition to silica, it contains calcium, magnesium, and iron. Actinolite is a non-hazardous relative of asbestos and is a common mineral in metamorphic rocks.
olivine	Silicate mineral containing iron and magnesium, (MgFe)2SiO4. It is the main component of the upper mantle. A green glassy mineral formed at high temperature. Common in basalt, especially ocean-floor basalt, and in ultramafic rock. Gem-quality olivine is called peridote. Rock made up entirely of olivine is called dunite.
garnet	Family of silicate mineral containing varying amounts of aluminum, iron, magnesium, and calcium. Schist and gneiss often have tiny, glassy red garnet dodecahedrons.
kyanite	An aluminum-rich, blue to light green silicate mineral. Kyanite form in metamorphic rocks at moderate temperature and high pressure.
sillimanite	An aluminum-rich silicate found only in metamorphic rocks that form at high temperature and pressure.
epidote	Family of silicate mineral containing mostly calcium, aluminum, iron and magnesium along with water. Epidote is apple green and generally form very small, stubby, prismatic crystal. It often occurs in vein or as a green coating on fracture surfaces. Most common in metamorphic rocks, but occasionally forms in igneous pluton that crystallize very deep in the crust.
serpentine	"A family of silicate mineral rich in magnesium and water, derived from low-temperature alteration or metamorphism of the minerals in ultramafic rock. Rocks made up of serpentine minerals are called serpentinite. Serpentine minerals are light to dark green, commonly varied in hue, and greasy looking; the mineral feels slippery."
talc	Magnesium silicate mineral, with water. Commonly called soapstone. Very soft and platy, like mica. Can be easily carved with a knife. Generally in very fine grained masses.
clay minerals	"Clay mineral are a group of complex and loosely-defined minerals containing aluminum and silica; they form from the alteration and weathering of primary silicate minerals"
bentonite	A clay material composed principally of the mineral montmorillonite. It has a great affinity for fresh water and when hydrated will increase its volume more than seven times. Water/bentoninte suspensions are essentially impermeable. Commonly used as a sealant for ponds.
illite	A potassium-rich clay mineral
smectite	Group of clay, those most susceptible to shrink-swell
chlorite	Family of platy silicate mineral containing various amounts of magnesium, iron, aluminum, water, and small amounts of other elements. Some mineralogists include chorites in the mica family because the crystal form small flakes. Commonly green.
zeolite	A class of silicate containing H=O in cavities within the crystal structure. Formed by alteration at low temperature and pressure of other silicates, often volcanic glass.
mineral precipitate	A mineral deposited from a water solution in pores or other openings in rocks. Chemical reaction with the surrounding rock, changes in pressure or temperature, or just drying up (evaporation) can cause a mineral to precipitate out of solution. Quartz vein are common products of mineral precipitation.
ionic bond	A bond formed between atom by electrostatic attraction between oppositely charged ions.
bond	The force that holds together two atom in a compound. It may be derived from the sharing of electron (covalent) or from electrostatic attraction between ions.