Week 2 Flashcards
Mineral
A naturally occurring, inorganic, solid element or compound with definite chemical composition and a regular internal crystal structure. Minerals are usually naturally occurring.
Minerals can be made of one type of element (diamond or carbon), metals (gold, silver, or copper), or compounds of several different elements (clays of Al, Si and other elements).
Three ways to form a mineral
- Crystallization from a magma
- Crystal growth in the solid-state (minerals changing after nucleation)
- Precipitation from solution
Crystallization from a magma
A mechanism by which crystals form. As magma cools, minerals begin to form.
Crystal growth in the solid state
A mechanism by which crystals form. Minerals change after initial nucleation.
Precipitation from Solution
A mechanism by which crystals form. This occurs when a substrate is reached in an aqueous solution. (Example: salt in salt lakes)
Ionic Bonding
A type of bonding between cations (positively charged) and anions (negatively charged). Most minerals are ionicly bonded.
Covalent Bonding
Covalent bonds are formed when electrons are shared.
Classes of Minerals
Native Elements Oxides Halides Carbonates Sulfates Silicates Sulfides
Oxides defining Anion
Oxygen ion O2-
Halides defining ion
Chlorine Cl-, flourine F-, Bromine Br-, Iodide (I-)
Carbonates defining ion
Carbonate ion (CO3 2-)
Sulfates defining ion
Sulfate ion SO4 2-
Silicates defining ion
Silicate ion SiO4 4-
Sulfides defining ion
Sulfide ion S2-
Silicates
The most abundant mineral (composing 95% of the minerals in the crust).
Feldspar (60%) and Quarts (15%) are the most abundant.
These minerals are classified by:
- the linking of silica tetrahedral
- their composition (ferromagnesian or aluminosilicates, or the type of interlayer cations (in feldspars - Na+, Ca2+, K+)
Ferromagnesian Silicates
Silicates rich in Fe or Mg
Aluminosilicate
Silicates rich in Al or Si
Silicate ion
A central silicate ion surrounded by 4 oxygen atoms in a tetrahedron - this will form in a silicate tetrahedra arrangement
Polymerize Silicate formation types
The (SiO4)4- anion can polymerize by sharing oxygen corners into pairs, rings, chains, sheets, or frameworks
Silicate Structures
Single Tetrahedron, Single Chain, Double chain, Sheet, Network/Framework
Ferromagnesian Minerals
Minerals are composed of Iron or Magnesium ions which serve as cations to bind the silica tetrahedra together (usually dark in colour).
Very easy to weather as they form out of magma at very high temperatures. Typically, they weather (ex: oxidize) to form Fe/Al hydroxides as secondary mienrals.
Aluminosilicates
Also known as clays, such as feldspars. Clay particles are formed from the alteration of aluminum silicates in both felsic and mafic rocks.
Properties most clay minerals have in common
Most clay minerals are:
- Proposed of predominantly silica and aluminum
- less than 2 micrometers in size (clay fraction)
Non-SIlicates are classified to:
Non-silicates are classified in according to:
- the chemical composition of the anion
- the type of cation
Common non-silicate minerals
native elements, carbonates, sulfates, sulfides, oxides, hydroxides, halides
Carbonates
The carbonate ion (CO3 2-) consists of a carbon atom surrounded by 3 oxyden anions which are linked together by cation (Ca2+, Mg2+, Fe2+, or Mn2+).
Calcite
The most abundant carbonate, CaCO3, and is a constituent of limestone and marble.
Carbonates examples
Ca2+ calcite
Mg2+ dolomite
Fe2+ siderite
Mn2+ rhodochrosite
Sulfates
The basic structure of a tetrahedron is made up of a central sulfur atom surrounded by 4 oxygen anions (SO4 2-).
Example: gypsum (CaSO4)
Gypsum
CaSO4
Forms in evaporitic environments
Sulfides
Consists of the sulfide anion (S2-)
A chief mineral in metal ores. Example: pyrite (FeS2)
Hydroxides and Oxides
Compounds in which O2- or OH- is bonded to metal cations.
This group is the primary source of Fe, Al, Mn, and Ti.
Generally, hydroxides form from a solution and convert into oxide phases to be more stable.
Examples of Hydroxides and Oxides
Ferric hydroxide Fe(OH)3 Hematite Fe2O3 Magnetite Fe3O4 Gibbsite Al(OH)3 Corundum Al2O3 Mn-oxides MnO2 Rutile TiO2
Mineral Properties
Hardness Cleavage Fracture Luster Color Streak Density Crystal Habit
Hardness
An approximate measure of how readily a mineral scratches.
A mohs scale is used to measure hardness
Strong chemical bonds result in hard minerals. Covalently bonded minerals are generally harder than ionically bonded minerals.
The hardest mineral is diamond and the softest is talc.
Cleavage
Cleavage is poor if bonds in the crystal structure are strong, and good if bonds are weak. covalent bonds generally give poor or no cleavage. ionic bonds are weaker and therefore give good cleavage.
Fracture
Related to the distribution of bond strengths across irregular surfaces other than cleavage planes
Luster
Tends to be glassy for ionic crystals and more variant for covalent
Color
Determined by ions and trace elements. Many ionically bonded crystals are colorless. Iron tends to colour strongly.
This is not a good indicator as it varies due to chemical impurities.
Streak
The color of fine mineral powder is more characteristic than that of massive minerals because of uniformly small size grains.
This is good for hematite as it makes a red streak.
Density
Depends on the atomic weight of atoms or ions and their closeness of packing in the crystal structure
Crystal Habit
Depends on the plane of a mineral’s crystal structure and the typical speed and direction of crystal growth.
Acid Test
If putting acid on a mineral makes it fizz, the mineral contains carbonate.
Rocks
Naturally occurring aggregates of minerals
