minerals introduction what are they? physical properties & identification atoms & elements...
TRANSCRIPT
MINERALS
• Introduction• What Are They?• Physical Properties & Identification• Atoms & Elements• Mineral Groups
Minerals
Introduction
GEOL 131: Minerals - Intro
Eight Most Abundant Elements in Earth’s Crust
GEOL 131: Minerals - Intro
Some of the Most Abundant Minerals in Earth’s Crust
• Quartz
• Feldspars
• Micas
GEOL 131: Minerals - Intro
Some of the Most Abundant Minerals in Earth’s Crust
• Amphiboles
• Pyroxenes
• Olivine
GEOL 131: Minerals - Intro
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MineralsMinerals
What Are They?
Minerals Are:
• Solid
• Naturally occurring
• Inorganic
GEOL 131: Minerals – What Are They?
Minerals Have:
• Well-defined chemical compositions
• Well-ordered atomic structures
GEOL 131: Minerals – What Are They?
Minerals
Physical Properties & Identification
Physical Properties
• Each mineral has a unique set of properties
• Determined by mineral’s chemical composition and atomic structure
• Properties are used to identify unknown minerals
GEOL 131: Minerals – Physical Properties & Identification
Physical Properties Commonly Used in Identification
• Color• Streak• Luster• Cleavage • Crystal habit• Striations• Hardness• Effervescence• Magnetism
GEOL 131: Minerals – Physical Properties & Identification
COLOR
GEOL 131: Minerals – Physical Properties & Identification
Quartz
• Easy to observe, but can be misleading• Impurities can produce different colors
STREAK• Color of powdered mineral• More reliable than “bulk” color
GEOL 131: Minerals – Physical Properties & Identification
Streak plate
LUSTER• How sample reflects light• Not the same as color
GEOL 131: Minerals – Physical Properties & Identification
METALLIC luster NONMETALLIC luster
LUSTER• How sample reflects light• Not the same as color
GEOL 131: Minerals – Physical Properties & Identification
Both of these minerals have a METALLIC luster
CLEAVAGE
• How sample cleaves (breaks)
• Always the same for a given mineral
• Three aspects– Quality– Number of directions– Angle
GEOL 131: Minerals – Physical Properties & Identification
CLEAVAGE QUALITY - None
GEOL 131: Minerals – Physical Properties & Identification
No cleavage: irregular breakage surface
CLEAVAGE QUALITY - GoodGEOL 131: Minerals – Physical Properties & Identification
Good cleavage: somewhat regular breakage surface
Note “stair-step” pattern
CLEAVAGE QUALITY – Excellent/perfectGEOL 131: Minerals – Physical Properties & Identification
Excellent cleavage: smooth breakage surface
# OF CLEAVAGE DIRECTIONS
GEOL 131: Minerals – Physical Properties & Identification
• A number
• Only applies to good or excellent cleavage quality
# OF CLEAVAGE DIRECTIONS - OneGEOL 131: Minerals – Physical Properties & Identification
One smooth surface
# OF CLEAVAGE DIRECTIONS - TwoGEOL 131: Minerals – Physical Properties & Identification
Two non-parallel smooth surfaces
# OF CLEAVAGE DIRECTIONS - ThreeGEOL 131: Minerals – Physical Properties & Identification
Three non-parallel smooth surfaces
# OF CLEAVAGE DIRECTIONS - Four
GEOL 131: Minerals – Physical Properties & Identification
Four non-parallel smooth surfaces
Fluorite
CLEAVAGE ANGLE• Angle between cleavage surfaces
GEOL 131: Minerals – Physical Properties & Identification
90-degree angle 60-degree angle
120-degree angle
CRYSTAL HABIT
GEOL 131: Minerals – Physical Properties & Identification
• How a mineral grows
• Unusual to see well-formed crystals in nature– Need space to grow
CRYSTAL HABITGEOL 131: Minerals – Physical Properties & Identification
Well-formed crystal faces
Poorly-formed crystals: not enough space
CRYSTAL HABIT• Don’t confuse a crystal face with an excellent
cleavage surface
• Crystal face – caused by growth
• Cleavage surface – caused by breaking
GEOL 131: Minerals – Physical Properties & Identification
STRIATIONS• Thin grooves on mineral’s surface
• Can be hard to see
GEOL 131: Minerals – Physical Properties & Identification
From www4.uwm.eduFrom facweb.bhc.edu
HARDNESS
GEOL 131: Minerals – Physical Properties & Identification
EFFERVESCENCEGEOL 131: Minerals – Physical Properties & Identification
Dilute hydrochloric acid (HCl)
If CO3 ion present,
carbon dioxide bubbles will form:
CaCO3(calcite) + 2HCl =
H2O + CO2 + CaCl2
MAGNETISM• Some iron-rich minerals are magnetic
GEOL 131: Minerals – Physical Properties & Identification
Magnetite (Fe3O4) attracting a magnet
MINERAL IDENTIFICATION
• Table or flowchart
• Observation of unique properties
• Narrow down possibilities
GEOL 131: Minerals – Physical Properties & Identification
MINERAL IDENTIFICATION
GEOL 131: Minerals – Physical Properties & Identification
Minerals
Atoms & Elements
All Minerals Are Made of AtomsGEOL 131: Minerals – Atoms and Elements
GEOL 131: Minerals – Atoms and Elements The Periodic Table of the Elements
http://www.ptable.com/
Basic Structure of an AtomGEOL 131: Minerals – Atoms and Elements
Valence Shells
GEOL 131: Minerals – Atoms and Elements
Atomic Bonds
• Hold atoms together to make mineral crystals
• Formed by electron interaction
• Require filled valence shells
GEOL 131: Minerals – Atoms and Elements
Atomic Bonds
GEOL 131: Minerals – Atoms and Elements
Atomic BondsGEOL 131: Minerals – Atoms and Elements
Chemical Composition of Minerals
• Elements present and in what amounts
• Well-defined: Limited or no variation
• Described by mineral’s formula
• Halite (salt): NaCl
GEOL 131: Minerals – Atoms and Elements
Atomic Structure of Minerals
• Arrangement of atoms • Well-ordered: Repeats in a regular pattern
GEOL 131: Minerals – Atoms and Elements
Atomic Structure of Minerals
• Arrangement of atoms
GEOL 131: Minerals – Atoms and Elements
QUARTZ
Atomic Structure – Diamond vs GraphiteGEOL 131: Minerals – Atoms and Elements
GEOL 131: Minerals – Mineral Groups
MINERAL GROUPS
• Silicates (largest group)• Carbonates• Sulfates• Sulfides• Oxides• Halides• Native elements
GEOL 131: Minerals – Mineral Groups
MINERAL GROUPS - Silicates• Largest group
– 90% of Earth’s crust
• Si and O atoms in a tetrahedron (pyramid)
GEOL 131: Minerals – Mineral Groups
MINERAL GROUPS - Silicates• Oxygen atoms can bond to adjacent
tetrahedra in a mineral’s atomic structure
• Forms the “backbone” of the mineral
• Example: single-chain structure– Each tetrahedron shares two oxygens with
adjacent tetrahedra
GEOL 131: Minerals – Mineral Groups
MINERAL GROUPS - SilicatesSilicate structures
GEOL 131: Minerals – Mineral Groups
MINERAL GROUPS - Silicates
• A silicate mineral’s properties depend partly on its silicate structure
– Hardness: 3-D networks make harder minerals (quartz)
– Cleavage: sheet structures produce sheet cleavage (micas)
GEOL 131: Minerals – Mineral Groups
MINERAL GROUPS - Silicates
• Example: Hardness– 3-D frameworks make harder minerals
Quartz
GEOL 131: Minerals – Mineral Groups
MINERAL GROUPS - Silicates
• Example: Cleavage– Sheet structures produce sheet cleavage
Micas
GEOL 131: Minerals – Mineral Groups
MINERAL GROUPS - Silicates
• Dark vs. light silicates
– Dark: rich in Fe and Mg
– Light: little Fe or Mg
• Important for igneous rocks (next chapter)
GEOL 131: Minerals – Mineral Groups
MINERAL GROUPS - Silicates
• Some common silicate minerals– Quartz: SiO2
– Orthoclase feldspar (aka potassium feldspar or K-spar): KAlSi3O8
– Muscovite mica: KAl2(AlSi3O10)(F,OH)2
– Hornblende: Ca2(Mg, Fe, Al)5 (Al, Si)8O22(OH)2
GEOL 131: Minerals – Mineral Groups
MINERAL GROUPS – Carbonates• CO3 ion• Effervescence• Common examples
– Calcite: CaCO3
– Dolomite: CaMg(CO3)2
– Malachite: Cu2CO3(OH)2
Malachite
GEOL 131: Minerals – Mineral Groups
MINERAL GROUPS – Sulfates
• SO4 ion• Common examples
– Gypsum: CaMgSO4*2H2O
– Anhydrite: CaMgSO4
– Barite: BaSO4
Giant gypsum crystals, Naica Mine, Mexico
GEOL 131: Minerals – Mineral Groups
MINERAL GROUPS – Sulfides
• S, no oxygen• Important metal ores• Common examples
– Galena: PbS– Pyrite: FeS– Chalcopyrite: CuFeS2
Cubic galena crystals
GEOL 131: Minerals – Mineral Groups
MINERAL GROUPS – Oxides
• Oxygen• No Si, C, or S• Common examples
– Hematite: Fe2O3
– Magnetite: Fe3O4
– Corundum: Al2O3
Red corundum (ruby)
GEOL 131: Minerals – Mineral Groups
MINERAL GROUPS – Halides
• Cl, F, or Br• Common examples
– Halite (salt): NaCl– Fluorite: CaF2
Wieliczka salt mine, Poland
GEOL 131: Minerals – Mineral Groups
MINERAL GROUPS – Native elements
• Any element in pure form• Common examples
– Sulfur (S)– Graphite (C)– Copper (Cu)
End of Minerals chapter