All Terms (Topics 1-4)

Mineral

A substance that is naturally occurring (not made by people), inorganic, solid at normal temperatures, has a definite chemical composition, and an ordered internal structure

Family

Groups of minerals related by composition (eg. sulfides)

Group

Minerals with similar atomic structure (eg. garnet [A3B2(SiO4)3] which includes pyrope, almandine, etc.)

Series

Same structure but different composition; same structure but different composition (eg. olivine series is a continuous chemical variation between two species (solid solution): Mg2SiO4 (forsterite) and Fe2SiO4 (fayalite)

Species

Classically what we refer to as a “mineral” by its name

Polymorph

Same formula but different atomic structure (eg. low and high quartz)

Variety

Same mineral but distinctive physical property (eg. amethyst and rose quartz)

Native Elements

Minerals naturally composed of only one element, eg. diamonds

Silicates

Huge family of minerals that all contain some variant of SiO2 (eg. quartz)

Carbonates

Minerals containing CO3 2- anions (eg. calcite)

Oxides

Contains O 2- anions

Sulfides

Contains sulfur anions

Sulfates

Contains some variation of SO4 2- anions

Silicate Anion

SiO4, Si and O pack together to form a tetrahedron shape

Orthosilicates/Nesosilicates

Isolated tetrahedra with Si:O of 1:4, eg. olivine

Sorosilicates

2 tetrahedra linked by bridging oxygen: Si2O7 6- with Si:O 1:3.5, eg. hemimorphite

Cyclosilicates

Rings where tetrahedra have two bridging oxygens (BO): Si6O18 12- with Si:O of 1:3, eg. beryl

Inosilicates

Single chains where tetrahedra have 2 BO, formula of (SiO3)n 2n-, Si:O of 1:3 (n = infinitely repeating), eg. pyroxene

Double-Chain Inosilicates

Double chains where half the tetrahedral have 2 BO and 2 NBO and the other one has 3 BO and 1 NBO, (Si4O11)n 6n-, Si:O of 1:3, eg. anthophyllite

Phyllosilicates

Infinite sheets have 3 BO and 1 NBO, (Si2O5)n 2n-, Si:O of 1:2.5, eg. micas (sheets!)

Tectosilicates

3D networks where all corners are shared with 4 BO SiO2 with Si:O of 1:2, eg. quartz

Crystal

A crystal is a mineral, or another crystalline chemical compound (i.e. a solid with a specific chemical composition) with an external shape bounded by smooth plane surfaces

Euhedral

“Perfect,” describes a crystal (or mineral grain) what an excellent crystal shape, all the sides pretty much show a nice crystalline structure, eg. very nice-looking quartz crystal

Anhedral

Describes a crystal (or mineral grain) that lacks well-formed crystal faces (at least on the external faces, but the internal atomic arrangement same as the euhedral because… crystal), eg. sand grain

Subhedral

Describes a crystal 9or mineral grain) that are partly bound by good crystal faces, as well as faces that may have been crowded by adjacent mineral grains

Rocks

Any solid mass of mineral(s) or mineral-like matter that occurs naturally

Igneous

Formed through the cooling and solidification of magma or lava and mostly form homogeneous massive bodies, appear crystalline or glassy (crystal size depends on the rate of cooling)

Intrusive Igneous

Formed if it cools underground

Extrusive Igneous

Formed from lava on the surface

Sedimentary

Formed by the deposition and subsequent cementation of minerals or mineral-like substances and tend to be layered and some appear to be rocks composed of smaller pieces of rock cemented together

Metamorphic

Formed from the transformation of existing rock types when subjected to high heat (>150–200 C) and pressure (>100 MPa), and have evidence of recrystallization of foliation (have sort of a banded and folded texture)

Crystal Field Transitions

The interaction between the energy of white light and d orbitals of certain elements that are only partially filled by elections (promoting electrons to higher energy level, the d orbitals split, this is why different charges of ions form different colours based on the absorption)

Molecular Orbital Transitions

Results from the transfer of electrons between adjacent cations that have variable charges) in a crystal structure (non-localized electrons hopping around, so traces (transition metals usually) of other electrons not part of the main composition can be found in the mineral

Colour Centres

This refers to defects in mineral structures, such as ionic omissions (called vacancies) that may become filled with an excess electron to balance the charge of the missing ion (another electron goes to fill in the hole left by the missing electron), eg. fluorite

Streak

This is determined by scraping the mineral on a white porcelain streak plate, producing a small amount of powdered material on the surface

Diaphaneity

A measure of how much light can pass through a material

Transparent

Allows lights to pass through undistorted

Translucent

Light passes through but is bent and cannot resolve images

Opaque

No light passes through even the tiniest slice

Lustre

A measure of how the mineral reflects light

Adamantine

Superlative lustre (eg. diamond), very rare

Vitreous

Lustre is glassy (eg. quartz)

Dull/Earthy

Little to no lustre

Metallic

Lustre of polished metal; all of the light shone on it is reflected

Greasy

Lustre resembles fat or grease

Pearly

Type of lustre present in minerals with thin transparent coplanar sheets

Resinous

Lustre of resin, chewing gym or plastic

Silky

Lustre of long, parallel fibres that look like silk

Waxy

Lustre resembles wax

Submetallic

Lustre like metallic but a bit duller

Sheen

A measure of how light is reflected from within the mineral

Adularescence

Reflection from sub-microscopic inclusions (eg. moonstone)

Schiller

Reflection from exsolved layers in feldspars (eg. labradorite)

Iridescence

Reflection and interference from exsolved layers in labradorite (eg. more specific definition of schiller, like a subcategory?)

Play of Colour

Diffraction and interference of light through regular spacing of SiO2 spheres in opal

Crystal Habit

Refers to the general shape of a crystal or cluster of crystals, reflecting the ease of growth in a certain direction

Prismatic

Elongate habit with bounding faces forming a prism

Columnar

Habit of long, slender prisms

Acicular

Needle-like crystal habit

Tabular

Crystal masses that are flat like a board

Bladed

Crystal habit elongate and flare like a knife blade

Fibrous

Habit of thread-like masses

Dendritic

Habit is tree-like, branching

Sheeted/Laminar

Crystal habit is a layered structure with thin sheets

Drusy

A crystal habit with a surface that is covered with a subhedral crystals (eg. geodes)

Capillary

Hair-like or thread-like, extremely fine crystal habit

Radial/Stellate

Crystal habit of star-like radial aggregates

Massive

Crystal habit is shapeless, no distinctive external crystal shape, use when no other descriptor could really be applied

Equant/Stout

Crystal habit is equal in length, width and breadth

Double Terminated

Crystal habit with prismatic crystal with natural terminations on both ends

Striated

Crystal habit fine, slightly indented lines that are present on the faces of some crystals

State of Aggregation

The physical state and makeup of the mineral

Granular

Aggregates of anhedral crystals

Compact

Very fine grained so that the aggregation is not obvious

Botryoidal/Globular

Aggregates of grapelike, hemispherical masses

Mammillary

Smooth, rounded masses of aggregates

Reniform

Aggregates of intersecting kidney-shaped masses

Banded

Aggregates of minerals with bands of different colour or texture

Stalactitic

Aggregates form as stalactites, cylindrical or cone-shaped

Geode

Aggregates of a rock cavity filled with minerals

Oolitic

Aggregate mineral grains look like fish eggs

Pisolitic

Aggregates are rounded mineral grains the size of a pea

Crystal Form

Refers to the geometry of an euhedral crystal and is defined by angular relation between crystal faces, which depends on the internal arrangement of atoms

Cubic

Crystal form is cube-shaped

Hexagonal

Crystal form is 6-sided

Octahedral

Crystal form is 8-sided

Tetrahedral

Crystal form is triangular pyramid shaped

Dodecahedral

Crystal form is 12-sided

Twinning

Two or more single crystals of the same mineral intergrown symmetrically

Contact Twins

Twinned crystals that a single compositional plane (eg. quartz)

Penetration Twins

Complete crystals that pass through one another and often share the centre of their axial systems; classic for fluorite, pyrite, orthoclase

Polysynthetic Twins

Multiple layers of the crystal which grow in parallel layers, flashes of light, eg. calcite

Cyclic Twins

Twins with repeating symmetry for 360 degrees

Cleavage

Represents the breaking of a mineral along crystallographic planes, related to the regular atomic, internal crystal structure, and is a result of weak bonding or large interplanar spacing across atomic planes in a crystal structure

Basal/Platy Cleavage

Cleavage in one-direction, sheet-like

Prismatic Cleavage

Cleavage in two directions at right angles, uneven breaking in the front of the crystal

Cubic

Cleavage in three directions at right angle, eg. halite

Rhombohedral

Cleavage in three directions but not at right angles, eg. calcite

Octahedral

Cleavage in four directions

Parting

Breaking along planes of structural weakness caused by twinning or exsolution