L2: Minerals Flashcards
What is a mineral?
- Naturally occurring, inorganic, solid element or compound with a definite chemical composition and a regular internal crystal structure
- May consist of only one element or be compounds of many elements
What are the 5 points that define a mineral?
- Naturally occuring
- Inorganic
- Solid element/compound
- Definite chemical composition
- Regular internal crystal structure
In what 3 ways can a mineral form?
- Crystallization from magma (as magma cools, minerals begin to form)
- Crystal growth in the solid state (minerals can change after initial nucleation)
- Precipitation from solution (when a state of supersaturation is reached in an aqueous solution)
Cation
Excess positive charge
Anion
Excess negative charge
How can an atom be neutral?
If the # of protons = # of electrons
How do you form an ionic compound?
Combine cations and anions
Most minerals are _____ compounds.
ionic
What is a covalent bond?
Share electrons rather than donating or accepting them
Define polymorphs
Minerals with the same chemical composition but have different structures (ex. Diamond vs graphite)
What are the 2 types of minerals
- Silicates
- Ferromagnesian
Describe silicates
- Most abundant minerals in the continental crust
- Lighter colored rock
How are the minerals formed by silicates classified?
- The linking of the tetrahedral (i.e rings, chains, sheets, framework)
- Their composition
What minerals are abundant in the continental crust?
- Silicates
Feldspars (60%)
Quartz (15%)
All silicates make up 95% of minerals in the cruste
How does the basic building block work for silicates?
- (SiO4)^4 anion or tetrahedron = basic building block
- Can be present as isolated tetrahedra or can polymerize by sharing oxygen (“corners”) into pairs, rings, chains, sheets, or frameworks
Define ferromagnesian minerals?
- A group of minerals where Fe and Mg serve as the cations that bind the silica tetrahedra together
- The dark minerals in most rocks (black, brown, dark green)
How do clay minerals form?
Form from the alteration of aluminum silicates in both felsic and mafic rocks
What properties do most clay minerals have?
- Predominantly composed of silica and aluminum
2. Their size is < 2mm thus termed clay size fraction
What classifies non-silicates?
- The chemical composition of the anion
2. The type of cation
List some common non-silicates?
- Native elements – gold, silver, copper
- Carbonates – calcites (CaCO3)
- Sulfates – gypsum (CaSO4)
- Sulfides – pyrite (FeS2)
- Oxides – hematite (Fe2O3)
- Hydroxides – ferric hydroxide (Fe[OH]3)
- Halides – halite (NaCl)
What is calcite?
One of earth’s most abundant crust minerals
What are sulfides?
- The chief minerals in many metal ores
- Include compounds of the sulfide anion with metal cations
- Pyrite is the most common
What are hydroxides and oxides?
- Compounds of minerals in which O2- or OH- is bonded to metal cations
- They’re of great economic importance bc serves as a primary source of Fe, Al, Mn and T
- First form from solution and within time convert into more stable oxide phases
List and define the mineral properties.
Notes
List and define the characteristics of luster.
Notes
Rocks are _______ _______ aggregates of __________.
- Naturally occurring
- Minerals
Is color a reliable indicator of minerals? Explain why or why not.
- No!
- Color varies from specimen to specimen due to the presence of small amounts of chemical impurities that have nothing to do with the minerals basic composition
- Ex. quartz has many colors – clear, rose, smoky, amethyst
