Review for Exam Flashcards by Julia Morillo

What term describes the shape of a mineral in fine needle-like crystals?

Acicular.

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What type of fracture does quartz exhibit?

Conchoidal

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What term describes the tendency of certain minerals to split easily in certain regular directions?

Cleavage

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Which scale is used to measure the hardness of minerals?

Mohs’ Scale of Hardness

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What term describes minerals that can be beaten into new shapes?

Malleable

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How is the age of rocks estimated based on the severity of radioactive decay experienced by radioactive material present in the rocks?

Radiometric dating

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What property of minerals refers to their appearance in powdered form?

Streak

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What term describes minerals found in detached masses of spherical, ellipsoidal, or irregular shape?

Concretionary or nodular

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What is the term used to describe the property of minerals that allows them to return to their original shape after bending?

Elastic

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Which mineral property is described as the nature of a broken surface?

Fracture

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What apparatus can be used to measure the specific gravity of minerals or rocks that are not too small?

Walker Balance

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What term describes minerals that exhibit a kidney-shaped form?

Reniform

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Which mineral property is measured relative to a standard scale of ten minerals?

Hardness

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What term describes minerals consisting of spheroidal aggregations resembling a bunch of grapes?

Botryoidal

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What term describes minerals that exhibit a moss-like or tree-like form, generally produced by the deposition of a mineral in thin veneers on joint planes or in crevices?

Dendritic

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What term describes minerals with no lustre?

Dull

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What property of minerals refers to their weight relative to the weight of an equal volume of water?

Specific gravity

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What term describes minerals consisting of closely packed small crystals growing into a cavity?

Drusy

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What term describes minerals that show broad flat surfaces

Tabular

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Which mineral property refers to the appearance of a mineral surface in reflected light?

Lustre

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What term describes minerals that are capable of being cut with a knife?

Sectile

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What property of minerals is useful in distinguishing various oxides of iron?

Streak

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What term describes the response of a mineral to a hammer blow, cutting with a knife, and bending?

Tenacity

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What defines the geometric shape of minerals, which are bounded by faces arranged in a regular manner?

Crystals

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What are the angles between adjacent crystal faces for similar crystals of any particular mineral?

Constant

How many crystallographic axes intersect in a common origin within a crystal, defining the crystal faces?

Three or four

What divides a crystal into exactly similar halves, each being the mirror image of the other?

Plane of symmetry

How many classes of symmetry are defined by planes, axes, and centers of symmetry?

What is the smallest complete unit of pattern in the atomic structure of a crystal?

Unit cell

In which system are many crystals bounded by faces that are all similar?

Cubic System

What is a face in the Cubic System that cuts all three or more forms?

Pyramid

What are faces called in the Orthorhombic, Monoclinic, and Triclinic Systems that cut two lateral axes and are parallel to the vertical axis?

Prisms

What is a face that cuts any one axis and is parallel to the other two called?

Pinacoid

What term describes the phenomenon where two closely adjacent crystals have grown together with a crystallographic plane or direction common to both, but one reversed relative to the other?

Twin crystals

What is the ratio called when the angle of incidence is measured for air and is divided by the angle of refraction?

Refractive index (n)

What is the term for a mineral that divides a ray of light into two, resulting in two values of refractive index?

Doubly refractive or birefringent

What is the direction along which light entering a crystal is not split into two rays but passes through the crystal undivided called?

Optic axis

What is the property of minerals that have the same refractive index for light entering in any direction called?

Isotropic or singly refracting

What type of crystals have two optic axes and are therefore called biaxial?

Orthorhombic, Monoclinic, and Triclinic crystals

What are the two polaroids in a petrological microscope called?

Polarizer and analyser

What happens to the appearance of a slice of quartz cut perpendicular to the c-axis when viewed between crossed polars?

It appears completely black due to isotropy.

What is the difference in refractive index between the maximum and minimum values for a crystal called?

Birefringence

What phenomenon causes a slice of quartz cut obliquely to the c-axis to show a white or grey polarization color?

Birefringence

What is the term for a face in the orthorhombic crystal system that cuts all three or more forms?

Prism (pr)

What is the name for a face in the orthorhombic crystal system that cuts one lateral axis and is parallel to the other two?

Pinacoid (d)

What term describes a face in the orthorhombic crystal system that cuts one lateral and the vertical axis, and is parallel to the other lateral axis?

Dome

What phenomenon occurs when a ray of light traveling through one medium is bent or refracted upon entering another medium of different density?

Refraction

What is the constant ratio of sin i to sin r called when a ray of light passes from one medium to another?

Refractive index (n)

What is the refractive index for Canada balsam, and similar cements in which rock slices are mounted?

1.54

What term describes the property of a mineral that enables it to divide a ray of light into two?

Doubly refractive or birefringent

What is the direction in a calcite crystal along which light entering it is not split into two rays?

Optic axis

What type of minerals have only one value of refractive index for light vibrations traversing it?

Isotropic or singly refracting minerals

What are the two polaroids in a petrological microscope called, and how are they positioned?

Polarizer (below the stage) and analyser (above the stage), positioned at right angles to each other.

What is the term for the phenomenon where a birefringent mineral appears completely dark at intervals of 90° during rotation between crossed polars?

Extinction

How many times does extinction occur during each complete rotation of a birefringent mineral slice between crossed polars?

Four times

What is the term for the property of a mineral where extinction occurs when some crystallographic direction, such as its length or prominent cleavage, is brought parallel to a cross-wire?

Straight extinction

What is the term for the property of a mineral where extinction occurs when its length makes an angle with the cross-wire?

Oblique extinction

What term describes the phenomenon where some minerals exhibit a change of color when rotated above the lower polarizer on the stage of a microscope?

Pleochroism

What are minerals called that appear dark brown or black when viewed through a microscope due to their inability to transmit light?

Opaque minerals

How are opaque minerals illuminated when studied with a microscope?

They must be illuminated from above.

In which mineral group are the SiO4 tetrahedra arranged in pairs with aluminum atoms between them, separated by layers of potassium atoms?

Micas and other flaky minerals

What type of atomic structure is formed when each SiO4 tetrahedron is linked by all four oxygens, sharing them with adjacent groups?

Three-dimensional Frameworks

What method can be used to investigate the atomic structure of crystals?

X-ray analysis

Composition: (MgFe)2SiO4 Crystal System: Orthorhombic Color: Pale olive-green or yellow Lustre: Vitreous Fracture: Conchoidal Hardness (H): 6 Specific Gravity (G): 3.2 to 3.6 Pleochroism: Strong Extinction: Straight

Olivine

Composition: Enstatite - MgSiO3; Hypersthene - (MgFe)SiO3 Color: Dark brown or green (Hypersthene nearly black) Lustre: Vitreous to metallic Cleavage: Two good directions parallel to prism faces Hardness (H): 5 to 6 Specific Gravity (G): 3.2 to 3.5 Pleochroism: Enstatite weak, Hypersthene strong Extinction: Straight

Enstatite and Hypersthene (Orthorhombic Pyroxenes)

Composition: (CaMgFeAl)(SiAl)2O6 Color: Brown to black Lustre: Vitreous to resinous Twinning: Shows a re-entrant angle Hardness (H): 5 to 6 Specific Gravity (G): 3.3 to 3.5 Pleochroism: Generally absent or weak Extinction: Oblique

Augite (Monoclinic Pyroxene)

Composition: KAl2(Si3Al)O10(OH)2 Color: White (unless impurities present) Lustre: Pearly Cleavage: Perfect parallel to the basal plane Hardness (H): 2 to 2.3 Specific Gravity (G): About 2.9 Pleochroism: Strong Extinction: Straight

Muscovite (Mica)

Composition: (CaMgFeNaAl)2-3(AlSi)5-6O22(OH)2 Color: Dark brown or greenish black Lustre: Vitreous Cleavage: Two directions intersecting at 124° Hardness (H): 5 to 6 Specific Gravity (G): 3 to 3.4 Pleochroism: Strong in shades of green, yellow, and brown Extinction: Oblique

Hornblende (Amphibole)

Composition: K(MgFe)3AlSi3O10(OH)2 Color: Brown to nearly black Lustre: Sub-metallic or pearly Cleavage: Perfect parallel to the basal plane Hardness (H): 2.5 to 3 Specific Gravity (G): 2.8 to 3.1 Pleochroism: Strong, shades of brown and yellow Extinction: Parallel to the cleavage

Biotite (Mica)

Composition: KAlSi3O8 Crystal System: Monoclinic Color: White or pink Lustre: Vitreous Cleavage: Two good cleavages intersecting at 90° Special Features: Frequently twinned (Carlsbad, Manebach, Baveno) Hardness (H): 6 Specific Gravity (G): 2.56 Mean Refractive Index (R.I.): 1.52 Birefringence (Biref): Weak Extinction: Oblique

Orthoclase (Potassium Feldspar)

Composition: KAlSi3O8 Crystal System: Triclinic Color: White, pink, or green Lustre: Vitreous Special Features: Similar to orthoclase Hardness (H): Not specified Specific Gravity (G): Not specified

Microcline (Potassium Feldspar)

Composition: KAlSi3O8 Crystal System: Triclinic Color: Not specified Lustre: Not specified Cleavage: Not specified Hardness (H): Not specified Specific Gravity (G): Not specified

Anorthoclase (Potassium Feldspar)

Composition: Albite (NaAlSi3O8); Anorthite (CaAl2Si2O8) Crystal System: Triclinic Color: White or colorless (albite) to grey (anorthite) Lustre: Vitreous Cleavage: Not specified Hardness (H): 6 to 6+ Specific Gravity (G): 2.60 Mean Refractive Index (R.I.): 1.55 Birefringence (Biref): Weak Extinction: Oblique

Plagioclases

Composition: KAlSi2O6 Color: Not specified Lustre: Not specified Cleavage: Not specified Hardness (H): Not specified Specific Gravity (G): Not specified

Leucite (Feldspathoid)

Composition: NaAlSiO4 Color: Not specified Lustre: Not specified Cleavage: Not specified Hardness (H): Not specified Specific Gravity (G): Not specified

Nepheline (Feldspathoid)

Composition: SiO2 Crystal System: Trigonal Color: Colorless when pure Lustre: Vitreous Fracture: Conchoidal Special Features: No twinning, lack of alteration Hardness (H): 7 Specific Gravity (G): 2.66 Mean Refractive Index (R.I.): 1.553 (max), 1.544 (min) Birefringence (Biref): Weak Extinction: Straight

Quartz

Composition: SiO2 Color: White or brownish Lustre: Waxy Fracture: Conchoidal Special Features: Straight extinction Mean Refractive Index (R.I.): 1.54

Chalcedony

Composition: SiO2 Color: Black Fracture: Conchoidal

Flint

Composition: Hydrated silica (SiO2 · nH2O) Color: White, grey, or yellow Lustre: Pearly Fracture: Conchoidal Hardness (H): About 6 Specific Gravity (G): 2.2

Opal

Composition: ZrSiO4 Crystal System: Tetragonal Hardness (H): 7.5 Specific Gravity (G): 4.7

Zircon

Composition: Al2SiO5 Crystal System: Orthorhombic Color: Pink or grey Hardness (H): 7.5

Andalusite

Composition: CaTiSiO5 (with variations in composition) Crystal System: Monoclinic Hardness (H): 5 Specific Gravity (G): 3.5

Sphene (Titanite)

Composition: (Ca, Mg, Fe2+, Mn)3(Al, Fe3+, Cr)2(SiO4)3 Crystal System: Cubic Color: Pale pink Hardness (H): 6.5 to 7.5 Specific Gravity (G): 3.5 to 4.0 Special Features: Isotropic in thin section

Garnet

Composition: Complex, typically a boron silicate mineral Crystal System: Trigonal Color: Black, red, green, blue Hardness (H): 7 Specific Gravity (G): 3.0 Extinction: Parallel

Tourmaline

Composition: Mg2Al4Si5O18 Crystal System: Orthorhombic

Cordierite (Iolite)

Color: Shades of bluish-green and yellowish-green Lustre: Vitreous Hardness (H): 2 to 2.5 Specific Gravity (G): 2.65 to 3.0 Cleavage: Often observed Mean Refractive Index (R.I.): About 1.58 Birefringence (Biref): Weak grey

Chlorite

Color: Green, may be red if iron oxide is present Hardness (H): 3 to 4 Specific Gravity (G): 2.6

Serpentine

Color: White or greenish Hardness (H): 1

Talc

Composition: Kaolinite Color: White or grey Specific Gravity (G): 2.6

Kaolin (China Clay)

Composition: Ca2(Al, Fe)3(SiO4)3(OH) Color: Typically yellowish-green Hardness (H): 6 to 7 Specific Gravity (G): 3.4

Epidote

Colors: White or glassy G: Varies (Analcite: 2.25, Natrolite: 2.2) Crystal Systems: Cubic (Analcite); Orthorhombic (Natrolite)

Zeolites (Analcite, Natrolite)

These layers are formed by the linking together of tetrahedral SiO4 groups. The composition of this layer is typically Si2O5 or Si2O5(OH)4.

Tetrahedral Layers

These layers contain a metal ion (such as Al or Mg) surrounded by six hydroxyls arranged at the corners of an octahedron.

Octahedral Layers

Composition: Al2Si2O5(OH)4 Structure: Consists of stacked layers of silicon-oxygen sheets and aluminum hydroxyl layers.

Kaolinite

Structure: Built up of 3-layer units with variable water content. Absorption of water between the layers leads to significant swelling properties.

Montmorillonite

Composition: Variable, typically a mixture of potassium, aluminum, and silicon. Occurrence: Widely distributed in marine sediments, often found in shales.

Illite

Clay material Similar composition to kaolinite but with a different layer arrangement

Dickite

Often included with dickite and kaolinite, occurring as minute tubes.

Halloysite

A less common clay mineral.

Ilfite

typically mixtures of illite, kaolinite, and montmorillonite.

Sedimentary clays

often contain illite as the dominant clay mineral.

Shales

Structure: Cubic Properties: Colorless or nearly colorless varieties are valued as gemstones. Used as abrasives in granular aggregates (bort).

Diamond

Structure: Hexagonal Properties: Very soft mineral, used as a lubricant. Occurs in veins or lenticular patches.

Graphite

(Lead Sulphide): Crystals: Cubic

Galena

(Zinc Sulphide): Crystals: Cubic, often as tetrahedra

Sphalerite

(Copper Iron Sulphide): Crystals: Tetragonal

Chalcopyrite

(Iron Sulphide, "Fool's Gold"): Crystals: Cubic

Pyrite

Properties: Magnetic, soluble in HCl

Pyrrhotite

(Mercury Sulphide): Chief ore of mercury

Cinnabar

Occurs in deposits from the evaporation of saltwater bodies

Halite (Rock Salt, Sodium Chloride)

Oxides and Hydroxides

Haematite (Iron Oxide, Hematite): Crystals: Trigonal rhombohedral Ilmenite (Titanium Iron Oxide): Chief ore of titanium Magnetite (Iron Oxide): Crystals: Cubic Chromite (Iron Chromium Oxide): Crystals: Cubic Cassiterite (Tin Oxide): Chief source of tin Bauxite (Aluminium Ore): Source of aluminium

Carbonates

Calcite (Calcium Carbonate): Crystals: Trigonal Properties: Principal source of carbonate of lime. Recognized by perfect cleavage and its reaction with dilute acids. Aragonite: Orthorhombic Siderite (Iron Carbonate): Crystals: Rhombhedral Malachite (Copper Carbonate): Valuable ore of copper and ornamental stone.

What is the term used to describe weathering effects attributed to plants and animals?

Biological weathering

What term refers to the weathering effects caused by plants and animals, promoting the solvent action of water and the formation of organic acids?

Biological weathering

In which regions, characterized by rapid evaporation nearly equal to rainfall, can mineral deposits build up due to the retention of dissolved salts by capillarity?

Previously hot, semi-arid regions

Which classification system reflects the relationship between soil type and weathering type, based on climate?

Soil classification according to climatic zones

What are the agents capable of loosening, dislodging, and carrying particles of soil, sediment, and rock?

Agents of erosion (such as rivers, wind, moving ice, and water waves)

What term refers to the area drained by a river and its tributaries?

atchment or river basin

What topographical form is used to describe flat-topped hills resulting from partly denuded horizontal strata capped with hard rock?

Mesa

In erosion, what type of slope results when the rate of removal exceeds the rate of supply?

Convexo-concave slopes

If rock layers are inclined in one direction and the river flows parallel to the hard layers, what landforms are carved in the softer beds?

Long hollows or vales separated by ridges of harder rock, forming escarpments

What method estimates the age of rocks based on the severity of radioactive decay experienced by radioactive material present in the rocks?

Radiometric dating

How much does the ground's temperature increase with depth assuming no nearby sources of heat?

0.03 Celsius per meter or 30 Celsius per kilometer

What term describes the level of the sea or lake into which a river discharges?

Base-level

What is the term for the break in slope at the junction of the old river course with the new, deeper cut?

Nick-point

What are formed where a river flows over rocks of differing hardness, resulting in undercutting and the formation of overhanging ledges?

Rapids and waterfalls

What term describes the deposits laid down by rivers and may include fine material such as silt and mud as well as coarse sand and gravel?

Alluvium

What term refers to the deposits left on the old valley floor by a river after it cuts down its channel to lower levels?

Terraces

What structures, found in river-deposited and other shallow-water sediments, are known as current-bedding or cross-bedding?

Current-bedding or cross-bedding

What term describes the process where a river, after having deposited alluvium on a flood plain, cuts down its channel to lower levels, leaving remnants of earlier deposits on the old valley?

Rejuvenation

What term refers to the deepening of valleys during glaciations when sea levels were lower and rivers cut down into their valley floor to re-establish their grade?

Valley deepening

What type of deposits are usually very porous and compressible if rich in clay, and permeable if composed mainly of silt, sand, or gravel?

Alluvium

What term describes the term given to the situation where a river swings from side to side of its valley and eventually flows in big loops?

Meandering

What term describes the deposits laid down by rivers when they enter a body of water, such as a lake or the sea?

Deltas

What is the process called where each flood brings down sediment, and coarser material is dropped in front of the growing pile, building up foreset beds?

Sediment deposition

What term describes the deposits left on the old valley floor by a river after it cuts down its channel to lower levels?

Terraces

What is the term for the periodic rise and fall of the sea due to the pull exerted by the sun and moon on the globe?

Tides

What term describes a water movement that is quickly generated and soon over?

Tidal surges

What term describes wave motion produced when a water surface is swept by wind?

Wave motion

What type of waves are characterized by an up-and-down movement imparted to the water at the cliff face?

Reflected waves

What term describes waves that run in over a long distance in gradually shallowing water?

Storm waves

What coastal feature is formed at the base of many coastal cliffs, sloping gently seawards, and beveling off rocks of the foreshore?

Wave-cut platform

What types of coasts are the result of submergence, where there is a rise of sea-level relative to the land?

Submergent coasts

What term describes the process of the sea exerting a 'sawing' action at the base of cliffs, cutting a horizontal notch which weakens the cliff base?

Cliff erosion

What is the name for the isolated pillars of rock or sea-stacks formed when erosion in jointed rocks leaves behind resistant rock structures?

Sea-stacks

What type of coastline results from a rise of the land relative to the sea, eventually giving a nearly smooth coastline bordering an area of newly exposed sea-floor?

Coast of emergence

What term describes the deposits of very fine particles of mud that settle due to flocculation?

Settlement

What are the deposits of coarser particles built up at the angle of repose in water ahead of the growing pile of sediment called?

Foreset beds

What term describes the wave motion that diminishes with depth from the surface, ceasing almost entirely at a depth equal to the wavelength?

Wave interference

What is the name for the zone extending from the base of the cliffs down to low-water mark along the coast?

Shore

What are the waves characterized by interference with the sea floor and friction, resulting in a reduction in size before breaking?

Swell waves

What is the name for the zones in front of growing deltas where the finer material is deposited in the deeper water?

Bottomset beds

What term describes the rocks of the foreshore being exposed on a gently sloping platform formed at the base of coastal cliffs?

Wave-cut platform

What term describes the sandy ridge formed by longshore drift, extending out into open water from a bend in the coast?

Spit

What type of barrier forms when a spit extends across a bay, lying across the mouth of a small estuary, with a lagoon behind it?

Bay-bar or barrier

What are the elongated parallel islands composed essentially of sand, separated by inlets, called?

Barrier islands

What is the depth at which a balance exists between supply and dissolution rates, known as?

Calcite compensation depth

What type of sediment slowly accumulates on the ocean floor at rates of between 1 and 50 mm per 1000 years in the open sea?

Pelagic sediments

What term describes the nearly spherical forms with frosted surfaces that wind-blown sand grains become worn down to?

Eolian sand

What are the deposits of wind-blown fine particles separated from sand and carried over large distances called?

Loess

What notable feature associated with arid and wind-swept landscapes are residual peaks of hard rock left upstanding and wind polished above the general level?

Inselbergs (or 'island mounts')

What is the term for the work of denudation by wind, most prominently seen in regions with a hot, dry climate?

Wind erosion

What term describes the deposits of sediment laid down on the continental shelf by feeble currents out to sea?

Coastal marine deposits

What are the largest forms of desert dunes generally composed of?

Coarsest sand

What type of dunes have a crescent shape and are found in areas with a nearly constant wind direction and limited sand supply?

Barchan dunes

What is the wind-blown deposit known as loess primarily composed of?

Fine-grained calcareous clay or loam

What is the intermediate stage between snow and ice called?

Neve

What term describes the deposits left behind by a glacier or ice-sheet?

Glacial drift

What term refers to the debris dropped at the front of a glacier as the ice melts, forming a hummocky ridge?

Terminal moraine

What are the smooth oval-shaped mounds composed of boulder clay or englacial debris, sometimes molded over a roche moutonnee, called?

Drumlins

What term describes the tapered columns of soil each capped by a large stone or boulder formed by rain denudation in areas of thick soil containing embedded boulders?

Earth pillars

What is the general term used to describe the transport of material down a slope, including mechanisms like landslides?

Mass-movement

What term refers to the repeated, small-scale mass-movement on hills of hard rock that creates escarpments?

Colluvium

What percentage of the Earth was glaciated during the Pleistocene?

ore than one-third

What is the upward growth of a salt-marsh that accumulates further sediment called?

Salt-marsh accretion

What feature is formed when land ice meets the sea and begins to float and break up into icebergs?

Calving

What term describes the deposits of subglacial debris produced by melt water from the glacier?

Lodgement till

What term describes the wind-blown deposit composed of fine grained deposits of oceanic clay, wind-blown sand, and volcanic dust accumulating on the ocean floor?

Pelagic sediments

What term refers to the material held in the lower part of moving ice that acts as an abrasive, smoothing and polishing the underlying rock surface?

Englacial material

In what type of lakes did upland lakes often develop, dammed by the glacier of the main valley?

Hanging valleys

What type of dunes develop from small heaps of sand not less than 30cm in height and are found in areas where the wind blows from a nearly constant direction?

Barchan dunes

What are the deposits left behind by a glacier or ice-sheet called, which is generally thickest in valleys and lacks sorting and arrangement?

Glacial drift

What term describes the fine-grained laminated clays deposited in still water impounded in front of a retreating glacier or in glacial lakes?

Varves

Review for Exam Flashcards

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