Transcript Introduction to Minerals

Introduction to Minerals
And you thought you were finished
with chemistry 
What is a mineral?
1. Naturally occurring
2. Homogeneous solid
3. Definite, but generally not fixed,
composition
4. Ordered atomic arrangement
5. Inorganic processes
Mineral Examples: How are
compounds related to
minerals?
3. Definite composition:
SiO2
OR
FeS2
Mineral Crystal Shapes
4. Crystalline: 3D periodic arrays of precise
geometric arrangement of atoms
 Cut on the solid lines and fold on the
dotted lines
Mineral or Not?
At your table discuss whether or not the following
materials are minerals.
Be ready to justify your answers!
 Snowflake
 Coal
 Rock salt
 Window glass
 Graphite
 Oxygen
Mineral or Not…answers
Snowflake - Mineral
Coal - Not
Table salt - Mineral
Window glass - Not
Graphite – Mineral
Oxygen- Not
How do minerals form?
 There are four ways that minerals
form:
1.Crystallization within magma (i.e.
tourmaline, olivine, quartz, feldspar)
2.Precipitation from solution (salt flats)
3.Changes in pressure or temperature
4.Formation from hydrothermal
solutions
How are minerals classified?
 4,000 known minerals
 International Mineralogical Association
uses chemical composition to classify
minerals
 8 mineral classes that are categorized by
their anion group
8 mineral classes
1.
2.
3.
4.
5.
6.
7.
8.
Silicate (SiO2)
Carbonate (CO3)
Sulfate (SO4)
Halide (F, Cl, I, Br are most common)
Oxide (usually a single O or OH)
Sulfide (S is usually bonded to a metal = ores)
Phosphate (AO4 where A can be P, Sb, As, V
Element
How do you identify
minerals?
 Geologists rely on several simple tests to
identify minerals.
 These are based on physical and
chemical properties.
 How would you use the 8 identifying
properties to identify the minerals at
your table?
8 Identifying Properties:
1. Color: This is the most noticeable
characteristics of a mineral and the
least helpful
- This is determined by the
presence of trace elements in
certain compounds.
Ex: Quartz: these are all the same
2. Luster: The way that a mineral reflects light from
its surface.
- Described as Metallic or Non-Metallic
- Metallic – Reflect light like Gold,
Copper, Silver
- Non-Metallic – Calcite, Gypsum, Sulfur
Non-Metallic Luster
continued…
Most common Non-metallic Luster Descriptions:
1. Adamantine = brilliant like a polished diamond
2. Vitreous = glassy, like glazed porcelain or quartz
3. Resinous = yellow, dark orange, or brown like tree
sap
4. Pearly = Exhibiting a luster similar to the inside of
a mollusk shell or shirt button
5. Silky = minerals that have a very fine fibrous
structure
6. Earthy = dull, little reflection
3.Texture: Describes how a mineral feels
to the touch.
- Words to describe: Smooth, Rough,
Ragged, Greasy,
Glassy.
Smooth
Rough
4.Streak: The color of a mineral when it is
broken up or in powdered form.
- Usually rubbed against a porcelain plate,
which leaves a powder behind.
- Sometimes the external color doesn’t
match streak color.
- Streak hardly ever changes, even though
the colors of a mineral do
Pyrite: Streaks greenish
Gold: Streaks yellow
5.Hardness: a measure of how easily a mineral
can be scratched.
- Measured on the Mohs Hardness Scale –
Ranges from 1 – 10
1 = Softest
10 = Hardest
Talc = 1
Diamond = 10
Mohs Hardness Scale
Name
Hardness
Talc
Gypsum
1
2
Calcite
Fluorite
Apatite
Feldspar
Quartz
Topaz
Corundum
Diamond
3
4
5
6
7
8
9
10
Hardness of
Common Objects
Softest
Scratched by Fingernail
Scratch by Penny
Scratched by Nail
Scratched by Glass
Scratched by Steel File
Scratches quartz
Scratches Topaz
Hardest – Scratches
Everything
6. Cleavage and 7. Fracture: How a mineral will
break.
- Cleavage – a mineral that splits relatively
easily and evenly along one or more flat planes.
- Fracture – Minerals that break with rough or
jagged edges.
Fracture
Cleavage
8. Special Properties:
Magnetic, odor, reacts to an acid,
Tastes like salt, fluoresces, double
refraction,
Magnetite =
Magnetic
Sphalerite =
Smells like
rotten eggs
Calcite =
Reacts to HCL
Double Refraction- Calcite