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