Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Earth Rocks > Lab Midterm 1 > Flashcards

Lab Midterm 1 Flashcards

1
Q

What is a mineral?

A

A naturally occurring solid with unique internal structure, chemical composition, and physical properties.
Minerals may be attractive or have a useful physical property (e.g. diamonds, which look nice, but are also useful due to their hardness) or they may contain valuable elements.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

How are minerals and ores usually classified?

A

As metallic or nonmetallic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe metallic minerals

A

Occur in economically valuable ores of iron, copper, lead, zinc, etc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe nonmetallic minerals

A

Mainly “industrial minerals” such as gypsum and calcite. Nonmetallic minerals are also the main rock forming minerals.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are some common metallic minerals and their significance/use?

A
  1. Pyrite - commonly referred to as “fool’s gold”, almost always associated with metal ores, a source of sulphur for manufacturing sulphuric acid.
  2. Chalcopyrite - an ore mineral of copper (used to make wire)
  3. Galena - an ore mineral of lead (used in car batteries)
  4. Sphalerite - an ore mineral of zinc (used to galvanize iron)
  5. Magnetite - an ore mineral of iron (main ingredient of steel).
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are some common nonmetallic minerals and their significance use?

A
  1. Talc - talcum powder, insulators
  2. Gypsum - plaster, drywall (wallboard), chalkboard chalk, cement
  3. Calcite - flux in steel making, cement (lime)
  4. Halite - table salt, road salt, source of sodium and chlorine
  5. Graphite - lubricant, steel hardening, high tech metal
  6. Muscovite - insulators, “glitter in cosmetics
  7. Biotite - rock forming mineral
  8. Amphibole - rock forming mineral
  9. Orthoclase - rock forming mineral, gemstones (e.g. moonstone), ceramics
  10. Plagioclase - rock forming mineral, gemstones (e.g. labradorite)
  11. Quartz - rock forming mineral, gemstones (e.g. amethyst), glass, source of silicon metal used in computer chips
  12. Olivine - rock forming mineral, gemstone (peridot)
  13. Pyroxene - rock forming mineral
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the physical properties of minerals used to compare them/ distinguinsh?

A

Colour, streak, crystal habit, crystal form, lustre, diaphaneity, hardness, cleavage, and fracture mainly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe colour as a physical property of minerals

A

One of the most obvious physical properties, but unfortunately, not diagnostic for many minerals (with some exceptions)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe streak as a physical property of minerals

A

The colour of a mineral in powdered form, determined by rubbing it against a ceramic streak plate (e.g. graphite has a distinctive steel grey or black streak), used for minerals softer than 7 on the Mohs scale - some minerals won’t leave a streak because they don’t have a high enough hardness (?)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe crystal habit as a physical property of minerals

A

If a crystal grows in an unrestricted environment, such as in an open space or suspended in a liquid, it will develop crystal faces and a geometric shape which is a visible expression of the internal atomic structure. A few of these crystals include:
1. Cubic
2. Octahedral
3. Hexagonal
4. Rhombohedral
5. Dodecahedral

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe crystal form as a physical property of minerals

A

The characteristic external shape of the mineral. Common crystal forms are:
1. Equant - approximately equidimensional (calcite, halite)
2. Tabular - flat, tablet shaped (muscovite)
3. Columnar or prismatic-elongate (quartz)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe lustre as a physical property of minerals

A

The character of light reflected from a mineral.
1. Metallic: like a polished metal surface (pyrite)
2. Non-metallic:
- vitreous (like glass, e.g. quartz)
- resinous (like resin or maple syrup, e.g. sphalerite)
- pearly (e.g. muscovite - shiny and glass-like but with a warm “underglow” like a pearl)
- greasy (e.g. talc - looking like oil was smeared on the mineral surface)
- Other example are adamantine (brilliant), silky (asbestos) and earth. These are somewhat subjective terms but can be useful in some cases.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe diaphaneity as a physical property of minerals

A

The ability of a mineral to transmit light.
- opaque: all light is reflected (metallic minerals)
- translucent: some light is absorbed (orthoclase, most minerals)
- transparent: most light is transmitted through the mineral (muscovite)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe hardness as a physical property of minerals

A

The resistance of a mineral to scratching relative to Mohs Hardness scale of 10 minerals.
Commone hardness test tools: most people’s fingernails have a hardness of 2.5 (but can be slightly lower), copper pennies have a hardness of 3, a glass plate has a hardness of approximately 5.5., and the hardness of a ceramic (porcelain) streak plate is approximately 7.0.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the order of the Mohs hardness values for minerals?

A

1 Talc
2 Gypsum
3 Calcite
4 Fluorite
5 Apatite
6 Orthoclase
7 Quartz
8 Topaz
9 Corundum
10 Diamond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe cleavage as a physical property of minerals

A

The tendency of a mineral to break consistently along flat, parallel, smooth planes of weakness. The strength of chemical bonds among elements within minerals differs as a function of both chemical composition and crystal structure. When a mineral is broken, it tends to break between neighbouring atoms where bonding is weakest. When looking for cleavage, look for shiny, flat, broken surfaces (crystal faces can sometimes resemble cleavage surface, so be careful).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the types of cleavage?

A
  1. Basal cleavage - some minerals will break in only one dominant direction (e.g. muscovite or biotite, talc, gypsum). Note: minerals with basal cleavage will produces flakes if broken with a fingernail. *1 cleavage, 2 faces
  2. Prismatic cleavage (@ 90 or not @ 90 degrees) - two cleavage directions are represented in a broken specimen. For example, two cleavage directions will produce prism-like pieces of variable length (hence prismatic cleavage). Need to specific whether the cleavage angles are at 90 degrees or not. *2 cleavages, 4 faces (e.g. pyroxene, amphibole, feldspar)
  3. Cubic cleavage - three cleavage directions intersecting at 90 degrees produces a cube (thus cubic cleavage).
  4. Rhombohedral cleavage - Three cleavage directions not intersecting at 90 degrees, producing what looks like a leaning box - a rhombohedron. * 3 cleavages, 6 faces (e.g. calcite, dolomite)
  5. Octahedral cleavage - four intersecting cleavage directions at 90 degrees, will ideally produce an 8-sided polyhedron. * 4 cleavages, 8 faces (e.g. fluorite)
  6. Dodecahedral cleavage - six intersecting cleavage directions (not at 90 degrees) will ideally produce a 12-sided polyhedron. *6 cleavages, 12 faces (e.g. sphalerite)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Describe fracture as a physical property of minerals

A

A few minerals do not exhibit cleavage when broken, but rather fracture in a non-planar (but still distinctive) way.
1. Conchoidal fracture - smooth curved surfaces and concentric ridges (e.g. quartz) - see in broken glass, v common
2. Uneven - e.g. chalcopyrite
3. Fibrous - e.g. asbestos - rare
4. Hackly - sharp jagged edges and barbs - rare
* in some non metallic minerals (especially orthoclase feldspar), fracture surfaces can resemble cleavage surfaces if they are flattish. However, remember the cleavage surfaces tend to be highly reflective; those that are dull are likely to be fracture surfaces.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Other physical properties

A
  • Halite has a salty taste
  • Magnetite is attracted to a magnet
  • Calcite effervesces (fizzes) on contact with acid
  • Some minerals, such as plagioclase show striations (fine, parallel lines resembling scratch marks) on cleavage surfaces (e.g. plagioclase) or crystal faces (e.g. pyrite)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Describe the physical properties of Talc

A

mineral
- colour: beige/white (can be light green)
- streak: white to colourless
- diaphaneity: translucent
- lustre: pearly
- hardness: 1 (<2.5)
- cleavage: basal
Mg3Si4O10(OH)2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Describe the physical properties of Gypsum

A

mineral
- colour: white/ colourless
- streak: white/ colourless
- diaphaneity: translucent
- lustre: vitreous
- hardness: 2 (<2.5)
- cleavage: basal
CaSO4.H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Describe the physical properties of Calcite

A

mineral
- colour: beige/pink/ white (can be colourless)
- streak: white/ colourless
- diaphaneity: translucent
- lustre: vitreous/ pearly
- hardness: 3
- cleavage: rhombohedral (3 cleavages not at 90)
CaCO3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe the physical properties of Halite

A

mineral
- colour: yellow/white/ colourless
- streak: white/colourless
- diaphaneity: translucent
- lustre: vitreous
- hardness: 2.5-3
- cleavage: cubic (3 cleavages at 90)
NaCl

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Describe the physical properties of Quartz

A

mineral
- colour: white/pink/colourless
- streak: white/colourless/ none
- diaphaneity: translucent
- lustre: vitreous
- hardness: 7
- fracture: conchoidal (no cleavage)
SiO2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Describe the physical properties of Amphibole

A

mineral
- colour: black
- streak: white to grey
- diaphaneity: translucent
- lustre: vitreous
- hardness: 5.5-7
- cleavage: prismatic not at 90 (3 cleavages)
Ca2(FeMg)5Si8O22(OH)2 - ferromagnesium silicates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Describe the physical properties of Pyroxene

A

mineral
- colour: dark green/ orange/ black
- streak: white/ grey / greenish
- diaphaneity: vitreous
- hardness: 5.5-7
- cleavage: prismatic at nearly 90
(Mg1Fe)SiO3 - ferromagnesium sillicates - very similar to amphibole

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Describe the physical properties of Orthoclase

A

mineral
- colour: red/ white/ brown/ pink
- streak: white/ colourless
- diaphaneity: translucent
- lustre: vitreous
- hardness: 6 (5.5-7)
- cleavage: prismatic at 90 (3 cleavages)
(Potassium feldspar) KAISi3O8

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Describe the physical properties of Plagioclase Feldspar

A

mineral
- colour: grey/ white/ beige
- streak: white/colourless
- diaphaneity: translucent
- lustre: vitreous
- hardness: 5.5-7
- cleavage: prismatic not at 90 (3 cleavages)
NaAlSi3O8 -> CaAl2Si2O8 (silicate)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Describe the physical properties of Muscovite

A

mineral
- colour: brown/ white/ colourless
- streak: white/ colourless
- diaphaneity: transparent to translucent
- lustre: vitreous
- hardness: <2.5
- cleavage: basal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Describe the physical properties of Biotite

A

mineral
- colour: black/ brown
- streak: brown/white/grey
- diaphaneity: translucent
- lustre: vitreous/ pearly
- hardness: 2.5-3
- cleavage: basal
K(Mg, Fe)3AlSi3O10(OH)2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Describe the physical properties of Magnetite

A
  • colour: black/ grey
  • streak: black/grey
  • diaphaneity: opaque
  • lustre: metallic
  • hardness: 3-5.5
  • fracture: uneven
    Fe3O4
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Describe the physical properties of Pyrite

A
  • colour: gold (brassy yellow)
  • streak: grey/ greenish black
  • diaphaneity: opaque
  • lustre: metallic
  • hardness: 5.5-7
  • fracture: uneven
    FeS2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Describe the physical properties of Chalcopyrite

A
  • colour: gold (brassy yellow)
  • streak: greenish blac/ black/ grey
  • diaphaneity: opaque
  • lustre: metallic
  • hardness: 3-5.5
  • fracture: uneven
    CuFeS2
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Describe the physical properties of Sphalerite

A
  • colour: yellow brown / black
  • streak: orange/ brown/ yellow
  • diaphaneity: translucent
  • lustre: resinous
  • hardness: 3-5.5
  • cleavage: dodecahedral
    ZnS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Describe the physical properties of Galena

A
  • colour: dark silver/ grey
  • streak: black/ dark grey
  • diaphaneity: opaque
  • lustre: metallic
  • hardness: 2.5
  • cleavage: cubic (3 cleavages at 90)
    PbS
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Describe the physical properties of Graphite

A
  • colour: dark grey/ black
  • streak: dark grey/ black
  • diaphaneity: opaque
  • lustre: metallic
  • hardness: <2.5
  • cleavage: basal (too small to be observed)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Describe the physical properties of Olivine

A
  • colour: olive green/ yellow
  • streak: white/ colourless
  • diaphaneity: translucent
  • lustre: vitreous
  • hardness: 5.5-7
  • fracture: conchoidal (crystals too small to be observed)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What is an igneous rock?

A

A rock that solidified from mainly molten material (magma)

39
Q

What are the two origins of igneous rocks, and describe them

A
  1. Intrusive (plutonic): magma crystallizes slowly, deep below ground surface; rocks tend to have a phaneritic texture due to slow cooling
  2. Extrusive (volcanic): magma is extruded onto the ground surface where it becomes lava. Lava rocks usually have an aphanitic to glassy texture (due to rapid cooling). Explosive eruptions can produce large amounts of pyroclastic material - fragments of volcanic rock and fine-grained ash (produced by the pulverization of glassy material such as pumice).
40
Q

What are the main textures of igneous rocks?

A

There are two main textures observed in igneous rocks, as defined by the average size of their constituent crystals.
1. Phaneritic: interlocking crystals of about equal size that are easily visible to the unaided eye (visible)
2. Aphanitic: interlocking crystals, the overwhelming majority of which, are too small to see without a microscope; rock appears massive (i.e. structureless).
3. Glassy: can be considered as a sort of extreme version of aphanitic. Non-crystalline (amorphous) structure like glass. Obvious in solid, massive form (e.g. obsidian). May be difficult or even impossible to be directly observed in rocks showing vesicular or pyroclastic texture (in which the glassy material forms a fine meshwork or a solid mass of fine-grained particles.

41
Q

What are the special textures of igneous rocks?

A

Igneous rocks can have additional distinctive textures that provide information of how they formed. Generally occur in combination with aphanitic or glassy textures.
1. Porphyritic: >10% of the rock volume comprises large crystals (called phenocrysts) surrounded by a (usually) aphanitic matrix of smaller crystals (groundmass)
2. Vesicular: containing lots of holes (made by trapped gas bubbles). This texture commonly occurs in rocks also characterized by glass or aphanitic texture.
3. Pyroclastic (fragmental): composed of angular fragments of broken volcanic rock and fine-grained (dust-sized) ash particles that may be fused (welded) together. The poorly sorted, jumbled, nature of the particles can impart an “earthy” look that resembles concrete or clay brick.
- if the majority of the largest particles are < 4 mm in diameter, the rock is called tuff
- if the majority of the largest particles are > 4 mm in diameter, the rock is called volcanic breccia

42
Q

Describe mineralogy

A

Orthoclase, plagioclase, olivine, pyroxene, amphibole, quartz, and mica (biotite and muscovite) constitute over 95% (by volume) of all igneous rocks. As magma cools, these minerals crystallize in order according to Bowen’s Reaction series.

43
Q

List the minerals that crystallize at the highest temperature to the lowest temperature, based on Bowen’s reaction series (discontinuous series of crystallization)

A

Olivine (~1400-1100 degrees C)
-> Pyroxene (~1250-1000 degrees C)
-> Amphibole (~ 1100-800 degrees C)
-> Biotite mica (~1000- 800 degrees C)
-> Orthoclase (K-feldspar) ~750
-> Muscovite mica ~700
-> Quartz ~ 600

44
Q

Based on Bowen’s reaction series, describe the continuous series of crystallization

A

At ~1200 degrees C, Ca-rich rocks are those to first crystallize, then Plagioclase (50/50 Ca and Na), and finally the Na-rich rocks crystallize around 800 degrees C

45
Q

What is the composition (rock types) based on Bowen’s reaction series?

A

~1400-1200 degrees C = Ultramafic (periodotite/ komatite) - rare
~1200-1000 degrees C = Mafic (gabbro/ basalt) Mg + Fe, dark coloured
~1000-800 degrees C = Intermediate (diorite/ andesite)
~800-600 degrees C = Felsic (granite/ rhyolite) feldspar + silica, light coloured

46
Q

Describe the parent magma compositions

A
  1. Felsic: magmas rich in silica (and low in Fe and Mg content) produce high proportion of light-coloured minerals such as quartz, orthoclase (potassium feldspar) and Na-plagioclase feldspar, and tend to produce rocks that are light-coloured overall
  2. Intermediate: magma composition between felsic and mafic, producing rocks that are mid-way between light and dark overall
  3. Mafic: magmas rich in Fe and Mg (and lower silica content) produce high proportion of dark-coloured minerals such as pyroxene, amphibole, and Ca-plagioclase feldspar, and tend to produce rocks that are dark-coloured overall.
  4. Ultramafic (rare): magmas directly sourced from Fe-Mg rich mantle with very little modification in composition, producing nearly exclusively ferromagnesian (Fe, Mg-rich) minerals such as olivine (with olive green colour) and pyroxene (dark green to black colour)
47
Q

Tip for distinguishing felsic vs intermediate vs mafic in phaneritic and aphanitic rocks

A
  1. Phaneritic - composition can be determined by the relative proportions of light vs dark-coloured mineral crystals.
    - Felsic= light minerals > dark mineral crystals (note that pink to light red is still considered “light coloured”
    - Intermediate= light mineral crystals approx. equal to dark mineral crystals.
    - Mafic= dark mineral crystals > light mineral crystals
  2. Aphanitic - composition can be determined by the overall “tone” of the rock.
    - felsic= white to light grey or pink
    - intermediate= medium-grey
    - mafic= dark-grey to black
    *exception: obsidian. A natural volcanic glass that tends to be dark-coloured regardless or its composition (obsidian is usually black, even though it is almost always formed from felsic lava)
48
Q

Describe Granite

A

Igneous rock
- texture: phaneritic
- composition/ parent magma: felsic
- mineral content: potassium feldspar (orthoclase), quartz, biotite mica, some amphibole
*Na-rich

49
Q

Describe Rhyolite

A

Igneous rock
- texture: aphanitic
- composition/ parent magma: felsic
- mineral content: potassium feldspar (orthoclase), quartz, biotite mica, some amphibole
*Na-rich

50
Q

Describe Obsidian

A

Igneous rock
- texture: glassy
- composition/ parent magma: felsic (but dark coloured black)
- mineral content: potassium feldspar (orthoclase), quartz, biotite mica, some amphibole
*Na-rich

51
Q

Describe Pumice

A

Igneous rock
- texture: glassy + highly vesicular
- composition/ parent magma: felsic
- mineral content: potassium feldspar (orthoclase), quartz, biotite mica, some amphibole
*Na-rich

52
Q

Describe Diorite

A

Igneous rock
- texture: phaneritic
- composition/ parent magma: intermediate
- mineral content: plagioclase feldspar, amphibole, some quartz
*equal parts Na + Ca

53
Q

Describe Andesite

A

Igneous rock
- texture: aphanitic
- composition/ parent magma: intermediate
- mineral content: plagioclase feldspar, amphibole, some quartz
*equal parts Na + Ca

54
Q

Describe Basalt

A

Igneous rock
- texture: aphanitic
- composition/ parent magma: mafic
- mineral content: pyroxene, plagioclase feldspar, some olivine
*Ca-rich

55
Q

Describe Scoria

A

Igneous rock
- texture: Glassy + highly vesicular
- composition/ parent magma: mafic
- mineral content: pyroxene, plagioclase feldspar, some olivine
*Ca-rich

56
Q

Describe Gabbro

A

Igneous rock
- texture: phaneritic
- composition/ parent magma: mafic
- mineral content: pyroxene, plagioclase feldspar, some olivine
*Ca-rich

57
Q

Describe Peridotite

A

Igneous rock
- texture: phaneritic
- composition/ parent magma: ultramafic
- mineral content: mostly olivine (ferromagnesium material), some pyroxene
*Green

58
Q

What are sedimentary rocks?

A

Rocks composed of material derived from pre-existing rocks by processes of weathering, erosion, transportation, deposition, compaction, and cementation.

59
Q

How are sedimentary rocks classified?

A

Sedimentary rocks are classified into three main groups based on their compositional and textural characteristics:
1. Clastic (or detrital)
2. Chemical
3. Biochemical

60
Q

What are the compositional components of clastic sedimentary rocks?

A

Most common sedimentary rocks are clastic (detrital). These are largely composed of fragments/ particles of solid material weathered and eroded from pre-existing rocks. Precipitated minerals may occur in minor amounts as the cement that bind these grains together. Main components are:
- Rock fragments: from pre-existing rocks
- Mineral grains: rock fragments may further break down into their constituent mineral grains, and tend to be predominantly quartz (resistant to chemical and mechanical breakdown), and less commonly, grains of potassium feldspar or mica (usually muscovite) may be present.
- Clay: another mineral component in some clastic rocks. Clay is derived from the chemical breakdown of minerals such as feldspars. Clay mineral grains are too small to be visible, but the clay content can generally still be recognized from its dark colour (grey, brown or black) and earthy look, resembling hardened mud.
- Cement: the mineral cement that binds the grains of sediment together (due to their precipitation in pore between grains). Common cement materials are calcite, quartz and hematite.

61
Q

What is the importance of texture for clastic sedimentary rocks?

A

Because the composition tends to be rarely simple for clastic sedimentary rocks, texture (defined by grain/particle size) takes a more important role in the classification of these rocks.

62
Q

Describe Conglomerate

A

Clastic sedimentary rock
- sediment type: gravel; largest grains > 2 mm in diameter, clearly visbile to unaided eye. There may be a finer-grained (commonly sandy) matrix component between the larger grains.
Other important characteristics: largest grains show some degree of rounding of edges

63
Q

Describe Sandstone

A

Clastic sedimentary rock
- sediment type: sand; consists of well-sorted sand-sized grains 1/16 - 2 mm in diameter
Other important characteristics: surfaces feel obviously gritty (like sandpaper)

64
Q

Describe Siltstone

A

Clastic sedimentary rock
- sediment type: silt; consists of grains finer than sand but coarser than clay (1/256 - 1/16 mm), barely visible to the unaided eye.
Other important characteristics: surfaces have a “dusty” loo, but not as obviously gritty as sand.

65
Q

Describe shale

A

Clastic sedimentary rock
- sediment type: clay; consists of microscopic grains (< 1/256 mm in diameter) of clay minerals that are too small to see without high magnification.
Other important characteristics: commonly dark in colour (due to organic matter). Has “fissility” (splits readily into flat pieces)

66
Q

What are the compositional components of chemical sedimentary rocks?

A

Some chemical sedimentary rocks, such as rock salt (halite), rock gypsum (gypsum), and potash (sylvite) are deposited when the concentration of dissolved ions in seawater becomes too great to remain dissolved. The limestone that covers the walls in many caves is precipitated for similar reasons (dissolved components are forced to precipitate when their concentration reaches a critical point)

67
Q

Describe the textures of chemical sedimentary rocks

A

Chemical sedimentary rocks usually have a crystalline texture, owing to the precipitation of their mineral components from water. In many cases, they are specifically microcrystalline (meaning that the crystalline nature of the rock can only be observed at a microscopic level). One exception is rock salt, which is commonly coarsely crystalline (crystals large enough to be viewed with the unaided eye).

68
Q

How do we name chemical sedimentary rocks?

A

We base their identification largely on their mineral composition (since most have the same crystalline texture and too fine to see the individual crystals). Rocks are named based on the predominant minerals present in them.

69
Q

Describe Travertine

A

Chemical sedimentary rock
*a chemical/ inorganic limestone
- predominant mineral: calcite
- texture (and other features): microcrystalline. Commonly shows subtle colour banding and/or pores formed from gases released by microbes. Relatively soft - can scratch and be scratched with a penny - hardness of 3)

70
Q

Describe Chert

A

Chemical sedimentary rock
- predominant mineral: quartz
- texture (and other features): microcrystalline. Commonly exhibits conchoidal fracture on broken surfaces. Very hard due to quartz content (can scratch glass)
*includes varieties flint (grey to brown) and jasper (red). Chert can also be biochemical.

71
Q

Describe Rock Gypsum

A

Chemical sedimentary rock
- predominant mineral: gypsum
- texture (and other features): usually microcrystalline. Looks very dense, but can be scratched with a fingernail. Commonly contains darker streaks of impurities

72
Q

Describe Rock Salt

A

Chemical sedimentary rock
- predominant mineral: halite
- texture (and other features): microcrystalline to coarsely crystalline. When coarsely, cubic cleavage should be apparent on freshly broken crystal surfaces.

73
Q

Describe biochemical sedimentary rocks

A

Some organisms can mediate the formation of minerals such as calcite for the purpose of constructing their skeletons (as in the case of seashells). When these organisms die, their skeletal materials become sedimentary particles, and can thus form biochemical (or sometimes called organic) sedimentary rocks.

74
Q

What are the compositions of biochemical sedimentary rocks?

A

The compositions of biochemical sedimentary rocks are rather limited as they reflect the compositions of the skeletal components of once-living organisms. A great many organisms make their skeletons (e.g. shells) out of mineral calcite. However, some others construct their skeletons out of silica or phosphate (e.g. teeth and bones of vertebrate animals).

75
Q

Describe the textures of biochemical sedimentary rocks

A

Some biochemical sedimentary rocks contain identifiable fossil skeletal remains of once-living things that are visible without the aid of magnification. The general term for these larger skeletal grains is bioclasts, and a rock containing a significant amount of these is said to have a bioclastic texture. Other remains may be microscopic, forming a homogeneous-looking, calcareous (calcite-rich) mud (with particles too small to see with the unaided eye).

76
Q

How do we name biochemical sedimentary rocks?

A

Limestone is an example of a sedimentary rock that may be chemical or biochemical (travertine, is a chemical form).
- A dense, homogenous-looking limestone formed entirely from calcareous mud is called micrite (a term shortened from microcrystalline calcite).
- Chalk is a type of limestone that, similar to micrite, is very fine-grained, but is very crumbly/powdery.
- Fossiliferous limestone consists of bioclasts (usually fossil shells made of calcite) imbedded in a much finer-grained matrix of micrite (calcareous mud component).
- Coquina is sort of like an extreme version of fossiliferous limestone that is nearly entirely made of bioclasts cemented together (and looks rather like dry oatmeal).
- Coal is a biochemical sedimentary rock produced by the lithification of organic matter (typically derived from partly decomposed land plants).

77
Q

Describe Micrite

A

Biochemical sedimentary rock
Nearly 100% microscopic grains of calcite. Dense and homogenous-looking. Typically grey to tan in colour.

78
Q

Describe Chalk

A

Biochemical sedimentary rock
Nearly 100% microscopic remains of planktonic algae. Typically white, and crumbly/powdery. Dead plankton.

79
Q

Describe Fossiliferous limestone

A

Biochemical sedimentary rock
Bioclasts (usually fossil shells, whole or fragmented), in a micrite matrix. Matrix typically grey to tan in colour.

80
Q

Describe Coquina

A

Biochemical sedimentary rock
Nearly 100% bioclasts (usually fragmented fossil shells)

81
Q

Describe Coal

A

Biochemical sedimentary rock
Altered organic matter, mostly from land plants. Brown to black, commonly shiny, very lightweight.
Dead plant matter - fossil fuel.

82
Q

What are metamorphic rocks?

A

Metamorphic rocks are those produced by the transformation of one rock to another under the influence of heat and pressure.
The process of metamorphism can involve simple “cooking” of rock surrounding a body of magma (contact metamorphism) or can involve the combined influence of increasing heat and directed pressure (regional metamorphism).
Fluids also play an important part in the redistribution of ions that result in the formation of new minerals.

83
Q

What are the compositions of metamorphic rocks?

A

The composition of metamorphic rocks varies widely and is largely dependent on the mineral components of the parent rock (protolith). Some of the more common metamorphic include: quartz, muscovite mica, biotite mica, potassium feldspar and calcite.
When it occurs as crystals large enough to be directly observed with the unaided eye (about 0.5 mm or larger in diameter), muscovite mica is easily recognized by its light colour (silvery white) and basal cleavage. Muscovite crystals that are too small to be seen without high magnification impart a bluish grey colour and a shiny sheen to the rock.
Another mineral that commonly occurs in metamorphic rocks is garnet. Garnet crystals tend to have a round shape and commonly range from red to black in colour.

84
Q

Describe the textures of metamorphic rocks (contact vs regional metamorphism)

A

The textures of metamorphic rocks directly reflect the conditions under which they form, but are also influenced to some extent by their mineral content.
1. Contact metamorphism: is a local-scale phenomenon that occurs when an igneous intrusion “cooks” the rock surrounding it under relatively uniform pressures, platy and elongate minerals retain a random orientation. Regardless of whether or not the rock contains platy/elongate minerals, a rock formed in this way will produce a non-foliated texture.
2. Regional metamorphism: if the original rock (called parent rock, or protolith) is shale (most common sedimentary rock), increasing metamorphic grade (increases temperatures and pressures) impart different types of foliation.

85
Q

How do we name metamorphic rocks?

A

The naming of metamorphic rocks takes into account composition and texture.

86
Q

Describe Quartzite

A

Metamorphic rock
- mineral composition: quartz
- texture: non-foliated

87
Q

Describe Marble

A

Metamorphic rock
- mineral composition: Calcite
- texture: non-foliated

88
Q

Describe Slate

A

Metamorphic rock
- mineral composition: muscovite, quartz
- texture: Slaty cleavage
*dull

89
Q

Describe Phyllite

A

Metamorphic rock
- mineral composition: muscovite, quartz
- texture: Phyllitic foliation
*silky/satin

90
Q

Describe Schist

A

Metamorphic rock
- mineral composition: most common = mica (biotite and muscovite), quartz, and sometimes garnet
- texture: Schistose foliation
*very shiny

91
Q

Describe Gneiss

A

Metamorphic rock
- mineral composition: most common = potassium feldspar, plagioclase feldspar, biotite, amphibole, pyroxene, and sometimes garnet
- texture: Gneissic foliation
*light + dark bands

92
Q

What are the different kinds of foliation?

A
  • Slaty cleavage: characterized by the tendency of the rock to split into plate-like pieces (but mineral grains are too small to be visible). A rock exhibiting slaty cleavage is called slate.
  • Phyllitic foliation: similar to slaty cleavage, but has a silky/satiny sheen due to slightly larger (but still very tiny) mica crystals that are preferentially aligned. A rock exhibiting phyllitic foliation is called phyllite.
  • Schistose foliation: at a medium grade of metamorphism, micas become large enough that they sparkle in light in a rock called Schist
  • Gneissic foliation: at the highest grade of metamorphism, light and dark minerals tend to seperate into distinct compositional bands (alternating light and dark), forming the rock gneiss
93
Q

What about non-foliated metamorphic rocks?

A

Earth Rocks (1 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions