(2) Minerals Flashcards
What is a mohorovicic?
Where the oceanic and the continental crusts meet
Plate Tectonics
- Theory that considers the lithosphere as broken into plates that are in motion.
- IMPORTANT: provides framework for understanding many of the world’s dynamic geologic process. Past and present.
- Plates change sizes over millions of years
3 types of plate boundaries
Divergent, Convergent, and Transform
Divergent Plate Boundaries
- Plates move apart from each other.
- Magma rises from hot asthen to create new crust in the gap between the plates.
- Mechanism of successive separation of plates and filling with magma to produce new oceanic lithospheres
Convergent Plate Boundaries
- The plates are moving together.
- The less dense the plates will override the denser plate.
- The denser plate descends into the mantle (subducted).
- Oceanic crust is subducted beneath continental crust.
Transform Plate Boundaries
- Plates slide past each other.
- Plates scrape and deform as they pass each other.
- Results in earthquake along the boundary.
Minerals, Rocks, Sediment, Soil definition
- M: The basic building blocks of materials that make up the solid part of the earths surface.
- Rocks: a consolidated aggregate of one or more minerals
- Sediment: unconsolidated particles created by weathering and erosion of rocks.
Soil: an unconsolidated combination of minerals and organic material.
Why study minerals?
- Over 4000 known and new minerals are identified each year.
- 25-30 important rock-forming minerals
- Helps to understand the origin of rocks, soils, and sediments.
- Finding and exploiting natural resources.
- Predictive behaviors of materials.
What is a mineral?
- A naturally occurring inorganic solid.
- A chemical composition that i fixed or variable within a limited range.
- Uniform and constant chemicals and physical properties
- Has a definite crystal lattice structure.
Mineral Groups
- Native elements
- Silicates
- Carbonites : calcite, dolomite
- Oxides: hematite, magnetite, ice
- Sulphites: pyrite, galena, spalertite, cinnibar, chacopyrite
- Sulphates: anhydrite, gypsum, barite
- Halides: halite, sylvite, fluorite
Native Elements
Metals (Au, Cu,..), non-metals (C, S,..)
Silicates
- Most common rock forming minerals (about 1/3 of all minerals)
- Basic building block is the silicon oxygen tetrahedrum (SiO4)^-4
- Forms the SOT and plus one or more elements
- Arrangement in a crystal lattice depends on : sharing of oxygen atoms ; balance by positive ions
Silicate structures (arrangement of SOT and other elements)
- Isolated silicate structures are interconnected by cations
- Single chain structures share two oxygen
- Double chain structures share three oxygen
- Sheet structures share three oxygen and have weaker bonds since it connects as a sheet
- Network structures connect on any side (equidimentional)
Mineral characteristics are a function of..
.. Chemical composition AND the way the elements are arranged in a crystal lattice
Chemical composition of minerals
- Properties of the elements (size of ions, types of bonds, etc.)
- Some minerals consist of one element
- Most are compounds
- More than 100 elements, but most made up of only 8 (O, Si, Al, Fe, Ca, Na, K, Mg) in different combinations
- These 8 elements make up about 99% of Earth’s crust
Mineral Formation
- A tiny early crystal acts as a seed for a future growth
- Atoms migrate to the seed and attach to the outer face
- Growth moves faces outward from the centre
- Unique shape reflects the crystals internal shape
- Many minerals may take different forms (granular, aggregate, fibrous, etc
- BUT all forms of the same mineral will have the same lattice structure at the molecular level
- There are also MINERALOIDS (inorganic solids, but no crystal lattice. Glass, opal)
Physical Property: Crystal form
- A crystal is a solid with smooth planar faces whose orientations are determined by the lattice structure
- Angle between faces are consistent for a mineral (Steno’s Law)
- Internal lattices (silicate structures)
- Non-perfect crystals are more common, usually called grains
- Perfect crystals require no interference during growth from other minerals or changing conditions of temperature, pressure, etc.
Euhedral
Near- Perfect
Anhedal
Irregular
Physical Property: Colours (and Streak)
- Can be highly variable due to impurities/slight changes in compositions. Like Corundum
- Streak: colour of fine powder less variable than crystals
- Produced by scraping specimen on unglazed porcelain
- Most streaks are white, but some are distinctive
- Constrained by the hardness of porcelain
Physical Property: Luster
- Reflection of light from a surface
- Metallic: gold, copper, etc.
- Non-metallic: glassy, earthy, pearly, silky, etc.
Physical Property: Cleavage Breaks
- Directional breakage along planes pf weakness in lattice
- Breaks along smooth planar surfaces (cleavage planes)
- Number of directions : 1 dir = sheets, 2 dir = blocks, 3 dir = cubes, 4-6 uncommon (diamond has 4)
Physical Property: Fracture Breaks
When a mineral breaks along an irregular surface
Physical Property: Specific Gravity
Mass of substance/mass of equal volume of water
Physical Property: ‘Play of colours’
Rainbow iridescence due to arrangement of lattice (acts like prism)
Physical Property: Striations
Parallel lines on crystal faces due to minute changes in lattice orientation (pyrite)
Physical Property: Hardness (test)
- MOH’s scale of ‘scratchability’ a relative hardness scale
- 1 softest (scatch with a fingernail)
- 3 soft (scratch with penny)
- 5 medium (scratch with knife)
- 10 hardest (diamond)
Physical Property: Double Refraction
Refraction of light entering/leaving mineral creates double image
Physical Property: Tarnish
Weathering (usually oxidation) of mineral surface (Cu = green, Au = black)
Physical Property: Transparent, Translucent, and Opaque
- Transparent: clear and allows light to pass through
- Translucent: less clear but still allows light to pass through
- Opaque: light cannot pass through
Physical Property: Tenacity
Properties of molecules to resist separation
Physical Property: Brittle
Hard but liable to break of shatter easily
Physical Property: Malleable
Able to be hammered or pressed permanently out of shape without breaking or cracking
Physical Property: Ductile
Able to be drawn into a thin wire
Physical Property: Elastic
Able to resume its normal shape spontaneously after contraction or distortion
Physical Property: Taste/ smell
- Some minerals have distinctive tastes or smells
- Examples: Copper, Iron. Petroleum
Physical Property: Solubility, Radioactivity, and Phosphorescence/Luminescence
- Soluble in acids
- Has radioactive traits
- Glows or retains light
