Earth Materials 1 Test 3 Terms

Aluminosilicates

members of a family of compounds in which aluminum atoms substitute for silicon atoms in some of the silicon lattice sites of the silica structure.

Nesosilicates (Orthosilicates)

comprised of isolated tetrahedra. found in elements like garnet and olivine. have a silicon to oxygen ratio of 1 to 4 and have a charge of -4.

Cyclosilicates (Ring Silicates)

Silicates that have rings of silica tetrahedra in them. have a silicon to oxygen ratio of 6 to 18 and a charge of -12.

Single Chain Inosilicates

Silicates that have silicate tetrahedra are bonded in single chains and include pyroxenes. Possess a silicon to oxygen ratio of 1 to 3 and a charge of -4.

Double Chain Inosilicates

Silicates that have silicate tetrahedra are bonded in double chains. Includes amphiboles and have a silicon to oxygen ratio of 4 to 11 with a charge of -6. Sometimes known as "garbage can minerals" because they can incorporate volatiles and several cations into their crystal lattice.

Tectosilicates (Framework Silicates)

Silicates with tightly bound silica tetrahedra. Includes flint, chert, quartz, onyx, jasper, and feldspars. have a silicon to oxygen ratio of 1 to 2.

Phyllosilicates

Possess sheets of tetrahedra with a platy cleavage. Includes muscovite, biotite, chlorite, mica, and serpentine. have a silicon to oxygen ratio of 2 to 5 and 3 bridging oxygens for every non-bridging oxygen.

Sorosilicates

Rare silicates that form when silica tetrahedra link together to form a pair. have a silicon to oxygen ratio of 2 to 7 and a charge of -6.

Pyroxene (single-chain inosilicate) cleavage angles

87 and 93 degrees

Amphibole (double-chain inosilicate) cleavage angles

56 and 124 degrees

M1 bonds

Bonds in single chain inosilicates that from when a cation binds to a chain of silica tetrahedra that are facing each other. These bonds are stronger than M2 bonds, but are weaker than silicon-oxygen bonds.

M2 Bonds

Bonds in single chain inosilicates that form when a cation binds to a chain of silica tetrahedra that are facing away from each other. These bonds are weaker than M1 bonds.

expandable clays

clays with a charge between 0 to -1. They can expand like an accordian to allow water and other ions to be trapped between their layers.

Non-expanding clays

clays with a net charge of 0. they do not expand and are impermeable to water and other ions.

Micas

clays with a net charge of -1. have gaps between their layers that can trap cations.

Clay-group phyllosilicates

phyllosilicates that form from chemical weathering of minerals like feldspars. Includes Kaolinite, Talc, Smectite, Illite, and Montmorillonite.

Mica-group phyllosilicates

Phyllosilicates that can be differentiated between dioctahedral micas (have Aluminum) or trioctahedral micas (have Magnesium or +2 Iron). Includes Biotite, Chlorite, Muscovite, and Phlogopite. frequently found in medium-grade metamorphic rocks.

Double-Layer Phyllosilicates

Phyllosilicates that have two sheets of silica tetrahedra and a metal "filling" layer between them.

Dioctahedral Phyllosilicates

phyllosilicates that have two filled bonding sites and a third empty bonding site. these are filled by two +3 charge cations (ex. aluminum) in the metal "filling" layer between silica tetrahedra sheets.

Trioctahedral Phyllosilicates

phyllosilicates that have all three bonding sites filled. these are filled by three +2 charge cations (ex. magnesium or +2 iron) in the metal "filling" layer between silica tetrahedra sheets.

Exsolutions

Locations on a phase diagram where 2 phases can simultaneously exist.

Piezoelectric effect

describes the property of certain materials to create a voltage when they are mechanically deformed or when pressure is applied to them, such as in quartz.

solvus line

The locus of points on a phase diagram representing the limit of solid solubility as a function of temperature.

phase diagram

a graph showing the conditions at which a substance exists as a solid, liquid, or vapor.

Olivine (mineral)

A greenish colored magnesium iron nesosilicate (Mg,Fe)2SiO4 mineral common in ultramafic and mafic rocks.

Garnets

A group of nesosilicates that come in a variety of colors. Have a base of A (+2) 3 B (+3) 2 Si3O12. can be split into calcium and non-calcium garnets and form big, euhedral crystals. found in high-grade metamorphic rocks and lava flows.

Zircon

A very stable nesosilicate that commonly occurs in small amounts in granite. sometimes traps uranium inside of it that can be used for radiometric dating. Some are the oldest known minerals on earth.

Beryl

Cyclosilicate mineral that is sued as a source of beryllium. green colored beryl is known as emerald.

Tourmaline

Cyclosilicate accessory mineral found in granite, pegmatite, and gneiss.

miscibility gap

A region in a phase diagram in which two phases, with essentially the same structure, do not mix, or have no solubility in one another (i.e. no minerals can form).

Ternary diagram

A diagram that allows for the graphical representation of mineral chemistry in terms of three end-member components.

Wollastonite

Single-chain inosilicate mineral that forms when carbonate rocks with calcium carbonate get their carbon replaces with silicon.

Tremolite

Double-Chain Inosilicate that occurs in low-grade metamorphic rocks like dolomite.

Zeolite

Tectosilicates that can trap water and cations in their crystal lattices. Their crystal lattices have several cavities, tunnels, and chains of SiO2. Usually found in cavities or veins of igneous rocks or hydrothermally-altered minerals.

Feldspathoids

A group of minerals (e.g. leucite, nepheline, and sodalite) that are similar in composition to the feldspars, but contain less silica.

Eutetic Point

the lowest possible melting point of a mixture of two substances.

Peritectic point

The point on a phase diagram where a reaction takes place between a previously precipitated phase and the liquid to produce a new solid phase.

Quartz

Tectosilicate that can be brown, pink, white, colorless, or purple. lacks a cleavage due to its tightly-connected crystal lattice.

Opal

Hydrous, poorly crystalline material created via biomineralization. made of pure silica and forms several layers of small, interlocking spheres.

Antigorite

Variety of serpentine that has corrugated (alternating) bending between its silica sheets.

Chrysolite

Variety of serpentine that has continuous bending of its silica sheets. This creates fiber-like cylindrical tubes, which makes this serpentine an asbestiform mineral.

Lizardite

Rare form of serpentine that is undistorted.

Chlorite

Mica-group phyllosilicate that behaves like a non-expanding clay. It has a metal "filling" layer between its silica sheets and other metal "filling" layers.

Hydrolysis

The breaking down complex molecules by the chemical addition of water.

Non-Calcium Garnets

Includes pyrope, almandine, and spessartine.

Calcium Garnets

Includes Grossular, Andradite, and Uvarovite.

Hornblende

Black or dark green double-chain inosilicate that is commonly found in igneous and metamorphic rocks.

Glaucophane

Double-chain inosilicate with sodium. has a blue color and forms blueschists and metamorphic rocks in locations with low temperatures and high pressures.

Inosilicate "I-Beam" crystal lattice

chains of alternating silica tetrahedra and cations lock together to form interlocking "I-Beam" structures. The angles at which the "I-Beam" structures meet determines the angles of cleavage.

Al2SiO5 polymorphs

Nesosilicates that include Kyanite, Sillimanite, and Andalusite. They are typically found in medium to high-grade metamorphic rocks and have edge-sharing chains of aluminum octahedra.

Epidote Group

Group of sorosilicates with isolated and paired silica tetrahedra. have about 70 minerals and are relatively rare.

Chert/Flint

A rock (two types): sedimentary, composed of quartz with very fine crystalline texture.

Oswald Ripening

Process in which smaller crystals in a partial melt dissolve and recrystallize into larger crystals.

endmember

A pure mineral substance without solid solution

Chalcedony Quartz

A variety of quartz with fibrous veins inside of it.

reconstructive transformation

Occurs when the crystal lattice of a mineral gets broken apart and reorganized into a new mineral.

Inversions

low-energy transformations in minerals that occur at high temperatures and pressures. They are less extreme than reconstructive transformations as they don't completely tear apart the original crystal lattice.

Loam

perfect agricultural soil with equal portions of sand, silt, and clay.

Phlogopite Mica

Phyllosilicate with some iron in it. Can block ultraviolet light while permitting visible light to pass through.

Feldspars

The most abundant group of minerals in the earth's crust. form "crankshaft"-style chains with gaps that cations can squeeze into and form "polymorphs" with aluminum tetrahedra in different positions.

Diagenesis

the physical and chemical changes occurring during the conversion of sediment to sedimentary rock. Occurs between 100 to 200 degrees Celsius and at 1 atmosphere to 300 megapascals of pressure.

Metamorphism

the process in which one type of rock changes into metamorphic rock because of chemical processes or changes in temperature and pressure. Occurs at 200 degrees Celsius to the mineral's melting point and 300 to 1000 megapascals of pressure.

brucite sheet

Octahedral "filling" sheet in phyllosilicates with magnesium replacing aluminum atoms.

Plagioclase Feldspars

Includes feldspars that have a mixture of sodium and calcium, such as albite, oligoclase, andesine, labradorite, bytownite, and anorthite.