earth materials Flashcards
define a mineral
minerals are naturally occuring, homogenous, crytalline solid with a definite crystalline chemical composition
what is continuous and constant throughout the mineral structure.
• Atomic structure is continuous and constant throughout the mineral structure
define a rock
•a rock is a naturally formed aggregate of mineral matter constituting a significant part of the Earth’s crust.
what does consolidated mean?
it means the rock is firm
what does non-consolidated mean?
it means the rock is loose
what is concrete?
a non-natural aggregate of other rocks set in a matrix
coal, limestone, evaporite. are they biogenic or inorganic?
coal - biogenic
limestone - biogenic
evaporite - inorganic
define the unit cell and what it is representative of
• The Unit Cell is the smallest 3D repeating unit of crystal structure,
representative of :
• atomic structure
• chemical composition
• crystal symmetry
• It has regularly ordered atoms with fixed geometry
what is the length of an angstrom?
1A = 10-10m
cubic = …
CUBIC
a = b = c; α = β = γ = 90
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/964/559/a_image_thumb.png?1659415646)
tetragonal = …
TETRAGONAL
a = b != c; α = β = γ = 90
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/964/637/a_image_thumb.png?1659415646)
orthorhombic = …
ORTHORHOMBIC
a != b != c; α = β = γ = 90
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/964/650/a_image_thumb.png?1659415646)
monoclinic = …
MONOCLINIC
a != b != c; α = γ = 90 β > 90
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/964/653/a_image_thumb.png?1659415646)
triclinic = …
TRICLINIC
a != b != c; α != β != γ != 90
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/964/671/a_image_thumb.png?1659415646)
hexagonal
HEXAGONAL
a = b != c; α = β = 90; γ =120
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/964/687/a_image_thumb.png?1659415647)
trigonal - rhombohedral
TRIGONAL - Rhombohedral
a = b = c; α = β = γ != 90 < 120
crystal symmetry is defined by:
Crystal symmetry is defined by:
• Planes of symmetry
• Axes of rotation
• Axes of inversion
All properties of a crystal substance conform to a symmetry
symmetry is a defining property of…
Symmetry is a defining property of a crystal
if crystal growth occurs at the same rate in all directions..
If this occurs at the same rate in all directions the **shape of the unit cell will be retained in the macro crystals **
the symmetry of the macro crystals always reflects…
The symmetry of the macro crystals ALWAYS reflects at least the minimum symmetry of the crystal system of the unit cell.
name 9 properties of minerals to aid in the identification of them
- Habit of crystals and crystal aggregates
- Density
- Hardness
- Cleavage
- Colour
- Lustre
- Reactivity with acids
- magnetism,
- radioactivity
define habit
habit describes the general shape of a crystal or crystal aggregate
what controls crystal habit?
it is controlled by:
shape of the unit cell of the crystal
conditions under which the crystal formed.
what is nomenclature
they are terms to describe the form of naturally occuring minerals
what is the nomenclauture of this rock?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/969/676/q_image_thumb.jpg?1659453335)
prismatic habit
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/969/676/a_image_thumb.jpg?1659415647)
what is the nomenclauture of this rock?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/970/007/q_image_thumb.jpg?1659453335)
tabular habit (looks like tables on top of each other)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/970/007/a_image_thumb.jpg?1659415647)
what is the nomenclauture of this mineral?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/970/047/q_image_thumb.jpg?1659453335)
platy habit
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/970/047/a_image_thumb.jpg?1659415648)
what is the nomenclauture of this rock?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/970/133/q_image_thumb.jpg?1659453336)
fibrous habit
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/970/133/a_image_thumb.jpg?1659415648)
what is the nomenclauture of this rock?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/970/247/q_image_thumb.jpg?1659453336)
accicular habit
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/970/247/a_image_thumb.jpg?1659415648)
what is the nomenclauture of this rock?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/970/467/q_image_thumb.jpg?1659453336)
nodular radiating habit
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/970/467/a_image_thumb.jpg?1659415648)
what is the nomenclauture of ths rock?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/970/587/q_image_thumb.jpg?1659453337)
botryoidal habit
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/970/587/a_image_thumb.jpg?1659415648)
what is the nomenclauture of this rock?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/971/727/q_image_thumb.jpg?1659453337)
dendritic habit
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/971/727/a_image_thumb.jpg?1659415648)
when does twinning occur?
it can occur during crystal growth, or by the deformation during the formation of the rock
what is twinning?
twinned crystals have two or more parts that are physically continuous.
name the three typical types of twinning found in minerals
simple
repeat/ polysyntheitc
interpenetrant (two cubes penetrating each other)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/069/972/163/a_image_thumb.png?1659415649)
name two factors that effect density.
mass of the individual atoms
the packing of the atoms
where do fingernail, copper coin and steel knife blade come on the moh’s scale of hardness?
fingernail - 2.5
copper coin - 3.5
steel knife blade - 6.5
give the general hardness of these mineral groups
silicates
sulphides
oxides
carbonates, sulphates
Silicates 5 – 8
Sulphides <6
Oxides >6
Carbonates, sulphates <5
hardness generally increases with…
Hardness generally increases with density
Calcite CaCO3 D = 2.71 g/ml H = 3
Aragonite CaCO3 D = 2.93 g/ml H = 4
what is mineral cleavage?
mineral cleavage is the ability of minerals to split along well defined planes of weakness
cleavage planes represent planes of relative bond weakness in the crystal structure (distinct from rock cleavage)
whats the difference between cleavage and fracture?
fracture leaves an irregular pattern
fracture surfaces are uneven and not parallel to each other - unrelated to crystal structure e.g. quartz fractures but has no cleavage
cleavage has distinct regular patterns
what distinctive feature can you use to tell if it is a cleavage plane.
when the mineral brakes along the cleavage plane it will have a shiny/ reflective lustre due to the showing of a fresh plane of crystal.
if a mineral is idiochromatic we say that…
if a mineral is idiochromatic we say that the mineral has one distinctive colour that we can use to identify it. e.g native sulphur which is yellow
most minerals are allochromatic. this means…
most minerals are allochromatic. this means that the mineral can have variable colours due to different chemical or mineral impurities. e.g. quartz, flourite
this means that we shouldnt take colour as a major .factor in the identification of the rock
what is lustre?
lustre is the quality of light reflected and refracted by crystals.
__________ lustre is characteristic of transparent/ glassy minerals (i.e. most silicats, carbonates & sulphate minerals)
Vitreous lustre is characteristic of transparent/ glassy minerals (i.e most silicates, carbonates & sulphate minerals).
__________ lustre is characteristic of semi-transparent minerals
Resinous lustre is characteristic of semi-transparent minerals
_________ lustre is characteristic of opaque, highly reflective sulphide, oxide and native element minerals.
Metallic lustre characterises opaque highly reflective sulphide, oxide and native element minerals
________ lustre characterises very finely crystalline minerals
Earthy lustre characterises very finely crystalline minerals
________ lustre charaterises fibrous minerals
Silky lustre characterises fibrous minerals
what is luminescence?
- Emission of light when mineral is irradiated, e.g. by UV light or an electron beam
- Caused by defect in crystal structures or impurities
what is the difference between phosphorescence and fluorescence
Phosphorescence
Emission of light even after removal of UV radiation
Fluorescence (fluorite)
Emission of light only during UV irradiation
some of what type of minerals react with cold dilute HCL.
Some carbonate minerals react with cold dilute HCL and effervesce as carbon dioxide
which two minerals react with cold HCL?
calcite, aragonite (limestone) but other carbonate minerals only react in hot acid e.g. dolomite
name the most magnetic mineral
magnetite
which minerals have a high degree of radioactivity?
uranium and thorium
which two minerals have orthosilicate tetradhera structure?
garnet and olivine
which mineral is a chain silicate?
pyroxene
what are the two major types of pyroxenes and what is the diffence between the two?
Augite – stubby crystals - Ca clinopyroxene
aegirine –long crystals- Na clinopyroxene
for pyroxenes what two unit cell can they have and what name is then given to that mineral.
can be:
orthorhombic (orthopyroxenes)
monoclinic (clinopyroxenes)
give hardness, colour, habit, cleavage of pyroxene.
usually dark coloured but varies depending on Fe/Mg contents.
elongate prismatic habits but not acicular or fibrous.
intersecting cleavages at 87/93˚.
Hardness 5 – 6
define isomorphs
different chemical composition but same crystal structure
describe olivine interms of crystal, colour, cleavage, hardness and lustre.
olivines form equidimensional pale to dark green crystals
no apparent cleavage
hardness of 6½
victorious lustre
what is the unit cell of garnet? how can we tell?
cubic
as it has the same minimum symytery as a cube.
describe garnet in terms of crystal, colour, cleavage and hardness.
garnets form equi-dimensional dark crystals
no cleavage
hardness of 6 – 7½.
which mineral is a double chain silicate, linked lateally by various cations.
amphiboles
what are the two major types of amphibole?
hornblende
glaucophane (dark blue needle crystals)
ambibole and pryroxene look very similar to the eye.
how can we differentiate between amphibole and pyroxene?
easiest way is by looking at cleavage planes under cross section microscope.
amphibole has cleavage of 124/56º while pyroxene is more likely to be 90/90º
what habits can amphibole have?
elongate, acicular or fibrous habits.
describe amphiboles in terms of colour, cleavage, and hardness.
Fe/Mg varieties are dark coloured whereas the more Al rich varieties are light coloured.
cleavages at 124/56˚
Hardness = 5 – 6
what two minerals are sheet silicates?
mica
chlorite
what are the two major types of mica?
muscovite mica
biotite mica
whats the major difference between muscovite and biotite?
muscovite - usually colourless
biotite - dark brown (more black with more Fe)
![](https://s3.amazonaws.com/brainscape-prod/system/cm/070/490/800/a_image_thumb.png?1659415737)
what is the lustre, morphology, cleavage, hardness of both types of micas?
both muscovite and biotite have a pearly to vitreous lustre.
both exhibit a platy morphology; plates are flexible
one perfect basal cleavage
soft with a hardness of 2 to 3
what makes mica different to other silicates?
mica is much softer unlike other silicates
what is the unit cell of chlorites?
monoclinic
describe chlorites.
Chlorites are sheet silicates with a different crystal structure to that of the micas
In hand specimen chlorites are characteristically green in colour - green colour increases with increasing Fe contents.
They exhibit a platy morphology with one perfect basal cleavage
soft with a hardness of 2 to 3.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/070/490/849/a_image_thumb.png?1659415737)
name the two soft silicates and why?
micas and chlorites due to them being sheet silcates thus can bend very easily.
name two minerals which have a framework silicate
quartz
feldspar
what is the unit cell of quartz
trigonal
describe quartz
no cleavage
hardness = 7
vitreous lustre
conchoidal fracture
when identifying quartz what shouldnt you use to identify it?
you shouldnt use colour as you get many coloured varieties due to chemical impurities. however quartz is normally colourless.
what is chalcedony?
describe it properties in terms of fracture and hardness
micro-crystalline quartz with sub-microscopic pore spaces infilled with water.
They grow into a cavity. Can be used as thin blades used in surgery.
massive with concoidal fracture
hardness - 7
![](https://s3.amazonaws.com/brainscape-prod/system/cm/070/490/935/a_image_thumb.png?1659415738)