Science Olympiad Rocks and Minerals

igneous

rocks crystallized from hot, molten magma or lava, as it cooled

magma

hot, molten rock beneath the earth's surface

lava

hot molten rock that has flowed out and onto the Earth's surface

plutonic (or intrusive) rocks

A granular igneous rock that has solidified at great depth and shows distinct grain texture (e.g. granite, granodiorite)

volcanic (or extrusive) rocks

igneous rocks formed at the surface of the earth, formed from lava; balsalt, obsidian, rhyolite

texture (of a rock)

description of its grain size

felsic (or sialic) igneous rock composition

Rich in silicon, oxygen, and aluminum. Tends to have light-colored minerals such as quartz and potassuim feldspar. Examples: granite, rhyolite.

intermediate igneous rock composition

Intermediate in composition between felsic and mafic or between acidic and basic, having a silica content of between 54% and 65%. Mixture of light and dark minerals. Examples: diorite, andesite, syenite.

Mafic ignous rock composition

Iron and magnesium rich. Typically dark-colored. Examples: gabbro, basalt.

lithification

The process that converts sediments into solid rock by compaction or cementation.

strata

Distinct layers of rock. (Singular "stratum")

clastic rocks (detrital)

Sedimentary rocks are derived from the weathering of pre-existing rocks. The clastic texture is derived from broken or fragmental pieces.

evaporites

Sedimentary rocks that form from material left behind by the evaporation of water (usually seawater). Example: travertine - forms in caves and around hot springs.

carbonates

Sedimentary rocks formed through both chemical and biochemical processes. They include the limestones and dolostones. Minerals in carbonate rocks: calcite, dolomite, aragonite.

sedimentary

Rocks that consist of fragments from preexisting rocks or shells, usually carried by wind or water and then deposited in flat-lying layers or chemically precipitated.

non-clastic rocks

Sedimentary rocks formed from the precipitation of sea water.

organic sedimentary rock

Rock formed from the remains of plant materials.

metamorphic

Any rock (e.g. schist, gniess, etc) that was formed in some fashion from a preexisting rock, through heat, pressure, the effect of superheated fluids, or any combination of these forces.

foliated texture

Metamorphic rocks in which minerals are brought into line or layers due to heat and pressure, common for regional metamorphism, type of foliation can identify rock. Examples: slate, phyllite, schist, gneiss

non-foliated texture

Metamorphic rocks that lack layers; granular or massive. Common for contact metamorphism. Examples: marble, quartzite.

silky luster

mineral with fine fibers; example: gypsum satin-spar

waxy luster

resembles wax; example: chalcedony

earthy luster

resembles earthy materials like dirt, having no reflection; example: bauxite, clay, diatomaceous earth

hardness

the ability to withstand scratching

Moh's Hardness Scale

Relates 10 common minerals from hardest to softest. Higher numbered minerals can scratch lower numbered minerals.

streak

Color of a mineral in powdered form, created by scratching mineral on streak plate or unglazed porcelain.

cleavage

Tendency to break or separate along a flat surface due to a lack of or weakness in atomic structure. Minerals can have 1, 2, 3, 4, or 6 directions of cleavage. Example: muscovite, biotite.

cleavage plane

Flat surface created from cleavage breakage. Cleavage is further defined based upon its quality, with such modifiers as "perfect," "good," and "poor" being used.

striation

Thin, straight cuts on the cleavage plane, on crystal faces.

fracture

Surface created from breakage not related to atomic structure.

uneven fracture

Irregular, rough surface created from breakage not related to atomic structure.

conchoidal fracture

Curved, smooth surface created from breakage not related to atomic structure. Example: obsidian

contact metamorphism

Changes caused by proximity to magma or deep, hot rock.

regional metamorphism

Changes caused by intense stress and high temperatures.

hydrothermal metamorphism

Changes caused by hot liquids.

fault zone metamorphism

Changes caused by fault movement.

slaty texture

Foliated texture in rocks caused by low-grade metamorphism; dense rock containing very fine-grained mica minerals

phyllitic texture

Foliated texture in rocks caused by low-grade to intermediate-grade metamorphism; rock containing very fine-grained mica and chlorite mineral that form in a wave like manner, glossy luster, looks wrinkled, texture of phyllite.

schistose texture

Foliated texture in rocks caused by intermediate-grade metamorphism; medium to coarse-grained platy mineral such as micas, chlorite, and quartz present, texture of schist.

gneissic texture

Foliated texture in rocks caused by intermediate-grade to high-grade metamorphism rock containing layers of varying medium to coarse minerals, light and dark layers alternating, texture of gneiss.

migmatitic texture

Foliated texture in rocks caused by extreme heat and pressure, melting, rock containing igneous (granite) and metamorphic rock, texture of migmatite.

crystal form

The geometric shape of a crystal, can usually be observed at the surface of the mineral. There are 64 crystal forms separated into 6 classes: isometric, tetragonal, hexagonal/triagonal, orthorhombic, monoclinic, and triclinic.

crystallization

Liquid to solid phase change.

mass

the amount of stuff

matter

anything which has mass and occupies space

minerals

solid matter composed of elements in specific combinations and arrangements

rocks

composed of minerals in specific combinations

volume

how much space is occupied by a mass

clast

any fragment of rock debris, usually weathered from bedrock by mechanical processes

basal cleavage

one direction of cleavage; example: mica, clay, graphite

cubic cleavage

three directions of cleavage at 90 degrees; example: galena, halite

color banding

alternating layers of felsic (light colored) and mafic (dark colored) minerals common in high grade metamorphic rocks

conchoidal fracture

smooth, scalloped-shaped fractures common to quartz and other silica-rich minerals and rock (as well as plate glass), very common in obsidian

feldspar

A group of abundant rock-forming silicate minerals, including orthoclase and microcline (potash feldspars) and albite, oligoclase, andesine, labradorite, bytownite, and anorthite (the plagioclase, or soda-lime, feldspars. The feldspars form approx. 60% of the earth's crust.

fizz (HCl) test

Minerals containing calcium carbonate (CaCO3) will generally react, to varying degrees.

fossiliferous

any rock (usually sedimentary) that contains a large proportion of fossils

silicates

A group of minerals (e.g. quartz and orthoclase) based on the SiO4 tetrahedron. The vast majority of the earth's crust is igneous rock, and silicates are the most common mineral class in igneous rocks.

Tink test

A simple field method of distinguishing between shale (sedimentary) and slate (metamorphic). Shale, being composed of piles of loose debris, goes "thunk" when dropped, while slate, being harder and more tightly inter-grown, goes "tink." DO NOT TRY THIS during a Science Olympiad Competition!

ultra-mafic

More mafic than mafic. Ultramafic igneous rocks are composed almost entirely of olivine and pyroxine, with no feldspar. The ultramafic are thought to originate within the upper mantle of the earth, and are very rare at the surface.

accessory mineral

A mineral that occurs in a rock in minute quantities, and does not affect the way the rock is named for classified.

alkaline rock

A rock containing more that average amounts of potassium- and sodium-bearing minerals.

alteration

Amy physical or chemical change in a mineral or rock subsequent to original formation; usually results in the formation of new minerals or in textural changes in the rock.

amorphous

Literally, "without form"; applied to rocks and minerals that lack definite crystal structure.

amphiboles

A group of closely related, dark-colored rock-forming silicate minerals (e.g. actinolite, hornblende, glaucophane, and tremolite).

amygdaloidal rock

A volcanic rock containing munerous gas cavities (amygdules) filled with such secondary minerals as calcite, quartz, and zeolites.

amygdule

A mineral-filled cavity formed in an igneous rock by escaping gas.

argillaceous

Containing or composed largely of clay (e.g. argillaceous shale, etc.)

basic rock

An igneous rock (e.g. gabbro) with low silica content and a gigh percentage of pyroxene, hornblende, and labradorite (see acidic rock, intermediate rock, and ultrabasec rock)

batholith

A huge body of plutonic rock that has been intruded deep into the earth's crust and later exposed by erosion.

bedding

The arrangement of sedimentary rocks in approximately parallel layers (strata, or "beds"), which correspond to the original sediments that formed the rock.

bituminous rocks

Rocks that contain (and sometimes smess of) asphalt, tar, or petroleum.

botryoidal

Restmbling a bunch of grapes; describes hematite and a number of other minerals in which very small radiating crystals are arranged in massive clumps, giving a surface covered with spherical bulges (from Greek botrys, "bunch of grapes")

carbonaceous

Conposed largely of organic carbon (i.e. carbon derived from plant and animal tissue.

caronates

Minerals (e.g. calcite) in which the carbonate radical (CO3) is an important constituent.

chemical sedimentary rock

A rock formed by chemical processes; gypsum is a chemical sedimentary rock, formed by chemical precipitaion.

clastic rock

A sedimentary rock that is made up of fragments of preexisting rocks, transported mechanically into the place of deposition.

clay

Any soft sediment or deposit that is very plastic when wet and consists of very fine-grained, micalike materials, mainly hydrous aluminum silicates.

crystal

A solid mass of mineral, having a regular geometric shape and bounded by smooth, flat surfaces (crystal faces).

crystal habit

The actual form of a crystal; determined by the shape and relative proportions of the crystal faces.

crystal symmetry

The repeat pattern of crystal faces, caused by the ordered internal arrangement of a mineral's atoms.

extrusive rock

An igneous rock that solidifies on the surface of the earth.

foliation

The laminated structure present in regionally metamorphosed rocks that results from segregation of different minerals into roughly parallel layers.

hardness

Resistance of a mineral to abrasion or scratching.

luster

The surface apperance of a substance, or the manner in which it reflects light.

massive mineral

A mineral that occurs either without any definite external crystal form or in poorly defined masses of small crystals.

pegmatite

An igneous rock of extremely coarse grain size. Usually found as dikes within a larger plutonic or metaporphic rock mass, pegmatites are often excellent sources of large, fine crystals, especially of quartz, tourmaline, tourmaline, feldspar, and mica.

phenocryst

A prominent crystal (in a porphyritic rock) surrounded by smaller mineral grains.

silica

Silicon dioxide (SiO2), a tremendously abundant mineral that occurs widely and in many forms, including quartz, chalcedony, opal, and chert.

slaty cleavage

A variety of foliation typical of slates and characterized by parallel arrangement of clay minerals.

sulfates

A group of minerals (e.g. gypsum and barite) in which the sulfate radical (SO4) is an important constituent

sulfides

A group of minerals (e.g. pyrite, galena, and sphalerite) in which sulfur is in combination with one or more metals (copper, iron, or zinc)

tenacity

The ability of a substance to resist separation.

ultrabasic rock

Any plutonic igneous rock (e.g. peridotite) with very low silica content (less than that of a basic rock) (see acidic rock, basic rock, and intermediate rock).

vitreous

Glasslike in appearance and texture.