Review for Exam Flashcards
What term describes the shape of a mineral in fine needle-like crystals?
Acicular.
What type of fracture does quartz exhibit?
Conchoidal
What term describes the tendency of certain minerals to split easily in certain regular directions?
Cleavage
Which scale is used to measure the hardness of minerals?
Mohs’ Scale of Hardness
What term describes minerals that can be beaten into new shapes?
Malleable
How is the age of rocks estimated based on the severity of radioactive decay experienced by radioactive material present in the rocks?
Radiometric dating
What property of minerals refers to their appearance in powdered form?
Streak
What term describes minerals found in detached masses of spherical, ellipsoidal, or irregular shape?
Concretionary or nodular
What is the term used to describe the property of minerals that allows them to return to their original shape after bending?
Elastic
Which mineral property is described as the nature of a broken surface?
Fracture
What apparatus can be used to measure the specific gravity of minerals or rocks that are not too small?
Walker Balance
What term describes minerals that exhibit a kidney-shaped form?
Reniform
Which mineral property is measured relative to a standard scale of ten minerals?
Hardness
What term describes minerals consisting of spheroidal aggregations resembling a bunch of grapes?
Botryoidal
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
What term describes minerals with no lustre?
Dull
What property of minerals refers to their weight relative to the weight of an equal volume of water?
Specific gravity
What term describes minerals consisting of closely packed small crystals growing into a cavity?
Drusy
What term describes minerals that show broad flat surfaces
Tabular
Which mineral property refers to the appearance of a mineral surface in reflected light?
Lustre
What term describes minerals that are capable of being cut with a knife?
Sectile
What property of minerals is useful in distinguishing various oxides of iron?
Streak
What term describes the response of a mineral to a hammer blow, cutting with a knife, and bending?
Tenacity
What defines the geometric shape of minerals, which are bounded by faces arranged in a regular manner?
Crystals
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?
32
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
