What is a Mineral?
• Naturally formed solid substance with a
crystal structure
What do All Minerals have in Common?
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Formed by Natural Processes
Are not Alive and Never Were Alive
Have a Definite Volume & Shape
Are Elements or Compounds with a Unique
Chemical Make-Up
• Are Crystals (particles arranged in patterns
that are repeated over and over)
How do Minerals Form?
Physical Properties Used to Identify
• Color
– Can be misleading
– Can vary due to impurities
Physical Properties Used to Identify
• Luster
– Surface Reflection
– Metallic = Shiny
– Non-Metallic = Dull
Physical Properties Used to Identify
• Streak
– The color of the powdered form of the mineral
– The color of the streak can be different than the
mineral
– Minerals must be softer than the streak plate
Streak - Quartz
• Quartz comes in many colors, but… the streak
is always white!
Physical Properties Used to Identify
• Hardness
– A measure of how easily a mineral can be scratched
• Mohs Hardness Scale
– 1 (Talc) = Softest
– 10 (Diamond) = Hardest
Simple Hardness Test Method
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Test more than one area of each sample
Fingernail: Hardness less than 2
Glass: Hardness = 5.5
If you can make a scratch in the mineral with your
fingernail:
– Hardness < 2.
• If you cannot make a scratch in the mineral with
your fingernail, but the mineral cannot make a
scratch in the glass:
– 2 < Hardness < 5.5
• If the mineral scratches the glass:
– Hardness > 5.5
Physical Properties Used to Identify
• Cleavage and Fracture
– Atomic arrangement determine the way the
mineral breaks
• Cleavage: Minerals break along smooth, flat
surfaces and every break has the same general
shape
• Fracture: Minerals break with random, jagged
edges
Mica
• Mica cleaves in thin sheets, because the
weakest joints are between flat sheets of
strongly-joined atoms.
Galena
• Galena cleaves into cubes, because the joints
inside are equally strong.
Gold
• The “nugget” shape of gold is a good
representation of random fracture.
Physical Properties Used to Identify
• Density
– Reflects the atomic mass and structure of a
material
Mass
Density 
Volume
– If you had a sample of gold and a sample mica of
the same size, the gold would have greater weight
Physical Properties Used to Identify
• Specific Gravity – the ratio of the mass of a
substance to the mass of an equal volume of
water at 4 C.
Physical Properties Used to Identify
• Magnetism
– Minerals often have a
strong or weak
attraction to a
magnetic field.
• Most magnetic
minerals are opaque,
metallic-looking
minerals
Physical Properties Used to Identify
• Smell
– Sulfides smell like a struck match or rotten eggs
– Arsenic smells like garlic
• Taste
– Halite and Hanksite are salty
– Sylvite is bitter
• Texture
– Fluorite has a smooth texture
– Talc is greasy
Physical Properties Used to Identify
• Refractive Index
– When light travels from
one substance to another,
it bends
• Fluorescence
– Some minerals “glow”
when exposed to black
light
Groups of Minerals
• About 1,500 unique minerals have been
identified
• Geologists have classified minerals into groups
– Distinct Chemical Nature
– Specific Characteristics
Groups of Minerals
• Silicates
– Most abundant group
– Contain Silicon and Oxygen
– Strongly-bonded Tetrahedron Ions
Groups of Minerals
• Carbonates
– Composed of one or more metallic elements
combined with a Carbonate (CO3-)
– Typically transparent and lightly colored
– A common component of the earth’s inner crust
Calcite
Rhodochrosite
Groups of Minerals
• Oxides
– Compounds of Oxygen and a Metal
– Strong Chemical Bond – Very Hard and Dense
– Great sources of iron and rare metals
Hematite
Groups of Minerals
• Sulfides
– Sulfur and a Metallic Ion
– Highly symmetric, simple structures
• Low Hardness and High Specific Gravity
Galena
Pyrite
Groups of Minerals
• Sulfates
– Composed of Elements with a Sulfate Ion (SO42-)
– Delicate and occur near the earth’s surface
Barite
Gypsum
Groups of Minerals
• Native Elements
– Made up of a Single Element
– Highly Ordered Atomic Arrangment
Copper
Gold
What is a Gem?
• Mineral or rock that has value
– Usually rare
• Example:
– Mineral: Corundum
– Gem: Ruby
Mineral Uses – Building a House
Mineral Uses – In the Kitchen
Mineral Uses – Transportation
Mineral Uses – Medical/Dental