Minerals Flashcards
What 4 traits define a mineral?
- Naturally formed
- Inorganic
- Crystalline when solid
- Specific chemical composition
Define a crystal.
Any solid body growing with planar surfaces, where the angle between faces remains constant as it grows
What is ‘growth habit’?
The characteristic crystal form of a mineral
What are some examples of mineral growth habits?
Prismic, cubic, acicular, botryoidal, fibrous
Describe prismic mineral growth? Give an example
Hexagonal shape (e.g quartz)
Give an example of cubic mineral growth.
Galena
Describe acicular mineral growth.
Needle-like
Describe botryoidal mineral growth.
Grape-like
Give an example of fibrous mineral growth.
Asbestos
Are minerals one element or compounds?
Either, but most are compounds
What is cleavage (in a mineral)? Where is it usually?
The plane along which a mineral tends to break, usually a plane with weaker bonds
What type of bonds does galena have? What’s that bond like?
Ionic bonds
- Transfer of electrons between a metal and a non-metal
What type of bonds does Diamond have? What’s that bond like?
Covalent bonds
- Sharing of electrons between non-metals
What type of bonds does graphite have?
Strong covalent bonds in layers, weak Van der Waal forces between layers
What is the lustre of a mineral?
The quality and intensity of light it reflects
Name the 5 most important mineral lustres.
Metallic, vitreous, resinous, pearly, greasy
Describe a vitreous lustre.
Glassy
Describe a resinous lustre.
Look of dried glue/amber
Why is colour unreliable in mineral identification?
Can be unreliable due to small impurities
What is the streak of a mineral?
The colour of the thin layer left behind when the specimen is rubbed on unglazed ceramic plate
What does the Mohs scale measure?
Hardness
What is hardness?
A mineral relative resistance to scratching
What are the first and last minerals on the Moh scale?
- Talc
.
.
. - Diamond
What is specific gravity? How is it measured/
A property used to measure density.
- The weight of a substance in air divided by the weight of an equal volume of water
Name 5 more mineral properties.
Magnetism, taste, chemical reaction with acid, double refraction, fluorescence
What is the difference between megascopic textural features and microscopic ones?
Megascopic can be viewed with the unaided eye, microscopic require high magnification
What extra technique is used when viewing rocks under high magnification to better view their components?
The use of plane polarised light
What are the 3 main mineral groups?
- Silicates (most abundant)
- Carbonates, sulphates and phosphates
- Ore minerals, oxides and sulfides
Which two elements make up >70% of the weight of the earth’s crust?
Silicon and Oxygen
What is the basic building block of silicates? How is it structured?
A silicate tetrahedron, silicon at the centre with 4 covalently bonded oxygens
What two things can a silicate tetrahedron do?
- Form ionic bonds with other atoms/molecules
- Form covalent bonds with other tetrahedra
Where is Olivine common?
A common constituent of igneous rocks in oceanic crust and the upper part of the mantle.
What are the 2 types of chain silicates? Where are they both common?
Pyroxenes (single chains) or Amphiboles (double chains)
- Common in igneous rocks and difficult to differentiate between
What are sheet silicates commonly called? What’s their structure?
Micas - Each tetrahedra shares 3 O atoms
What’s the main difference between pyroxene and amphibole?
Pyroxene - cleavages at 90°
Amphibole - cleavages at 120°
Name 3 micas?
Muscovite, Biotite, Chlorite
______________ accounts for about 60% of all continental crust minerals.
Feldspar
What are the 2 most common types of feldspar?
Potassium (K) feldspar
Plagioclase feldspar
How are feldspars formed?
By a silicate tetrahedra sharing all its O atoms
What shape crystals does quartz form?
Six-sided (prismic)
What are fine grained quartz called?
Chalcedony
What 3 carbonate minerals are most common?
Calcite, Dolomite, Aragonite
Which carbonate mineral reacts vigorously to hydrochloric acid?
Calcite
What 2 Sulphate minerals are most common?
Anhydrite, Gypsum
What is the most important phosphate mineral? Why is it so significant?
Apatite, our bones and teeth are made of apatite
What are the two main types of Ore Minerals?
Sulphides and oxides
What features are common in a sulphide ore mineral?
Metallic lustres and high specific gravities
What are the 2 most common sulphide ore minerals?
Pyrite, galena
What are the 2 most common oxide ore minerals?
Magnetite, hematite
What 3 important things about the past can minerals tell us about?
- Temperature and pressure where they formed
- Climate
- Seawater composition (by studying evaporite minerals)
What is the order of Mohs hardness scale?
- Talc
Gypsum
(fingernail)
Calcite
(copper penny)
Fluorite
Apatite
(pocket knife / glass)
K-feldspar
Quartz
Topaz
Corundum
Diamond
What two minerals are softer than a fingernail on the mohs hardness scale?
Talc and gypsum
What mineral is between fingernail and copper penny on the mohs hardness scale?
Calcite
Which minerals are harder than a pocket knife/glass on the mohs scale?
K-feldspar
Quartz
Topaz
Corundum
Diamond
Which minerals are between copper penny and pocket knife on the mohs hardness scale?
Fluorite
Apatite
