Week 1 and 2 Flashcards
What is a Unit Cell?
The smallest unit which, when repeated in 3D will build the crystal structure.
What are the 3 types of Unit Cell?
Simple Cubic, Body-centred Cubic and Face-centred Cubic
What is twinning?
Two separate crystals are inter grown and share some common points in the crystal lattice.
What are the 4 types of twinning?
Rotational, Simple, Multiple(lamellar) and Cyclic.
What is cleavage?
Where atoms are located at regular positions within the crystal lattice. Minerals can have single(sheet silicates) or multiple(pyroxenes and amphiboles) planes of cleavage.
What are mafic minerals?
Dark coloured minerals rich in Magnesium and Iron.
Eg Olivine, Pyroxenes, Amphiboles and Biotite.
What are Felsic minerals?
Light coloured minerals rich in Silicon and Aluminium. Eg Quartz, Feldspars and Muscovite.
What are isomorphic and polymorphic minerals?
Isomorphic- Different chemical composition but similar structure
Polymorphic- Same chemical composition but different structure
What is Homovalency and Coupled charges?
Homovalent- Same charges on both sides eg
Mg2+=Fe2+
Coupled- Same charges but in different quantities eg
Mg2+ + Ca2+= Al3+ + Na+
What are garnets?
Minerals commonly found in metamorphic rocks and colours reflect chemical composition
What are sorosilicates?
A silicate mineral sharing one apical oxygen commonly found in the Earths crust eg Epidote and pumpellyite.
What are single chain silicates?
Silicate minerals that join to form a single chain.
Minerals include Enstatite and Diopside (pyroxenes).
What are sheet silicates?
Silicate minerals that form a sheet like structure.
Minerals include Micas, Muscovites and Biotite.
What are double chain silicates?
Silicate minerals that form 2 conjoined chains.
Minerals include Glaucophane, Actinolite and Hornblende.
What are framework silicate?
Silicate minerals that form a stable crystal lattice.
Minerals such as Quartz are framework silicates.
What are the 2 types of feldspars?
Plagioclase(triclinic)- complete solid solution between Na and K end members eg Anorthite(CaAl2Si2O8) and Albite(NaAlSi3O8)
Alkali(monoclinic)-limited solid solution between Na and K end members eg Albite and Orthoclase/K feldspars eg microcline(KAlSi3O8)
What are the 2 types of oxide ore minerals?
Cubic - MgAl2O4(spinel) and FeFe2O4(magnetite)
Trigonal - Fe2O3(hematite) and Al2O3(corundum)
What are the 2 sulphide ore minerals?
Cubic 1 - PbS (galena)
Cubic 2 - FeS2 (pyrite)
What are the 4 types of carbonate minerals?
CaCO3 - calcite and aragonite
CaMg(CO3)2 - Dolomite
FeCO3 - siderite
Cu2CO3(OH)2 - malachite
What determines the mineralogy of a rock?
-Pressure/Temperature
-The chemical composition of the system
-Kinetic barriers to equilibrium
Why is Olivine unstable nearer the Earths surface?
Because it breaks down easily and also reacts with quartz to form a new mineral.
What are the controlling factors for stability?
Chemical thermodynamics - the energetically of chemical reactions
Kinetics - the rate at which chemical reactions take place
What are bedding planes and contacts?
Bedding planes - separate distinct sedimentary layers in a sequence of beds
Contact- any boundary that separates one rock from another
What is deposition and emplacement?
Deposition - the laying down of sediment carried by a fluid or gravity flow
Emplacement - the intrusion or eruption of igneous rock which may also form layers
What re the 4 stratigraphic principles?
Original horizontality - sediment layers are originally deposited horizontally
Superposition - oldest rocks are at the bottom and youngest at the top
Lateral continuity - sedimentary layers are laterally continuous over long distances and they don’t terminate abruptly unless eroded, deformed or thinned
Crosscutting relationships - any geological feature that cuts across existing rock is younger than the rock it cuts across.
What is dip and strike?
Dip - steepest angle between a tilted bed and a horizontal plane
Strike - the compass direction of the intersection between a bed and a horizontal plane
What are the 3 types of sedimentary rocks and their comprise of minerals?
Clastic - rocks made from pre-existing rocks( sandstones and mudstones)
Carbonate rocks - often consists of fragments of carbonate fossils but can be produced from precipitation of carbonates from water eg limestone
Chemical sediments - Evaporites, carbonates and FeM oxyhydroxides eg salt, gypsum and Dolomite
Minerals eg quartz, feldspars, micas carbonates evaporites and clays
What are the 2 types of metamorphism and what increase the grade of metamorphism?
Regional - rocks produced by burial associated with tectonic processes and pressure/temperature varies
Contact - rocks produced by heating around igneous intrusions usually at low pressures
Deformation of the rock during metamorphism causes the alignment of interlocking minerals and the grain size increase increasing the grade of metamorphism.
What minerals are usually found in metamorphic rocks?
Garnets,Micas, Feldspars, quartz, pyroxenes and amphiboles
What are the 2 types of igneous rocks?
Intrusive - rocks formed from magma that has not reached the surface and cools slowly underground
Extrusive - rocks formed from magma that has erupted on the Earths surface and cools relatively quickly
What is a grain, matrix and clast?
Grain : fragments of minerals
Matrix : fine-grained material holding everything together
Clast : fragments of rocks
What is a porphyroblast, porphyroclast and foliation?
Porphyroblast - new mineral grown through reaction
Porphyroclast - pre-existing mineral
Foliation - alignment of minerals
What is ground mass?
Fine grained material, usually glass and fine grained crystals.
What are the 7 crystal systems?
-Cubic
-Tetragonal
-Hexagonal
-Trigonal
-Orthorhombic
-Monoclinic
-Triclinic
