Introduction to Minerals

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Introduction to Minerals

• And you thought you were finished with chemistry ?

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Photos of really cool places!

• As we study rocks and minerals, remember these
  spectacular sites
• Think about how they formed
• Travel and ask questions!

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Why should we care?

• Salar de Uyini, Bolivia
• Worlds largest salt flat

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Antelope Canyon, AZ
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Zhangye Danxia Landform, Gansu, China
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Fly Geyser, NV
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Naica Mine, Mexico
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What is a mineral?

• Naturally occurring
• Homogeneous solid
• Definite, but generally not fixed, composition
• Ordered atomic arrangement
• Inorganic processes

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Mineral Examples How are compounds related to
minerals?

• 3. Definite composition
• SiO2 OR FeS2

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Mineral Crystal Shapes

• Crystalline 3D periodic arrays of precise
  geometric arrangement of atoms
• Cut on the solid lines and fold on the dotted
  lines

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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

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Mineral or Notanswers

• Snowflake - Mineral
• Coal - Not
• Table salt - Mineral
• Window glass - Not
• Graphite Mineral
• Oxygen- Not

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How do minerals form?

• There are four ways that minerals form
• Crystallization within magma (i.e. tourmaline,
  olivine, quartz, feldspar)
• Precipitation from solution (salt flats)
• Changes in pressure or temperature
• Formation from hydrothermal solutions

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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

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8 mineral classes

1. Silicate (SiO2)
2. Carbonate (CO3)
3. Sulfate (SO4)
4. Halide (F, Cl, I, Br are most common)
5. Oxide (usually a single O or OH)
6. Sulfide (S is usually bonded to a metal ores)
7. Phosphate (AO4 where A can be P, Sb, As, V
8. Element

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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?

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8 Identifying Properties

• 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

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• 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

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Non-Metallic Luster continued

• Most common Non-metallic Luster Descriptions
• Adamantine brilliant like a polished diamond
• Vitreous glassy, like glazed porcelain or
  quartz
• Resinous yellow, dark orange, or brown like
  tree sap
• Pearly Exhibiting a luster similar to the
  inside of a mollusk shell or shirt button
• Silky minerals that have a very fine fibrous
  structure
• Earthy dull, little reflection

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• Texture Describes how a mineral feels to the
  touch.
• - Words to describe Smooth, Rough,
  Ragged, Greasy, Glassy.

Smooth
Rough
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• 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 doesnt match
  streak color.
• - Streak hardly ever changes, even though the
  colors of a mineral do

Pyrite Streaks greenish
Gold Streaks yellow
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• 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

Diamond 10
Talc 1
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Mohs Hardness Scale
Name Hardness Hardness of Common Objects
Talc 1 Softest
Gypsum 2 Scratched by Fingernail
Calcite 3 Scratch by Penny
Fluorite 4 Scratched by Nail
Apatite 5 Scratched by Glass
Feldspar 6 Scratched by Steel File
Quartz 7
Topaz 8 Scratches quartz
Corundum 9 Scratches Topaz
Diamond 10 Hardest Scratches Everything
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• 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
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8. Special Properties Magnetic, odor, reacts
to an acid, Tastes like salt, fluoresces, double
refraction,
Sphalerite Smells like rotten eggs
Calcite Reacts to HCL
Magnetite Magnetic
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Double Refraction- Calcite