1. Minerals of Earth’s Crust
Chapter 3
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2. Mineral
A naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition.
Earth Science Chapter 3

3. Mineral Must occur naturally Formed by processes in natural world
Not manufactured (made by man)
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4. Mineral Must be inorganic Nonexample: coal
Not made of living things or the remains of living things
Nonexample: coal
Comes from the remains of plants and animals
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5. Mineral
Must be a solid
Definite (unchanging) shape and definite volume
Particles are tightly packed
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6. Mineral Must have a crystal structure
Has flat sides that meet at sharp edges and corners
Atoms arranged in regular, repeating pattern
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7. Mineral Must have a definite chemical composition
Always contains certain elements in the same proportions
Example: Quartz has one atom of silicon for every two atoms of oxygen
Pure, solid elements (mostly metals) are also minerals
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8. Physical properties of minerals
Result of chemical composition and crystalline structure
Useful for identifying minerals
Many can be seen with the eye
Others need tests and special equipment
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9. Color Easy to observe Not very useful Many have similar colors
Small amounts of impurities can dramatically change colors
Ruby and sapphire are both types of corundum
Weathered surfaces may hide color
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10. Streak Color of mineral in powdered form More reliable than just color
Tested by rubbing across a streak plate of unglazed ceramic tile
Streak color may be different than mineral color
Even though the color of a mineral may vary, its streak color is always the same
Minerals that are harder than streak plate leave no streak
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11. Luster Light that is reflected from a mineral’s surface
Metallic – like polished metal
Or nonmetallic
Glassy
Waxy
Greasy
Pearly
Submetallic or dull
Silky
Earthy
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12. Discuss Define “mineral” in your own words.
Amber is a precious material used in jewelry. It forms when the resin of pine trees hardens into stone. Is amber a mineral? Explain.
What does the phrase “definite chemical composition” mean?
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13. Density The amount of mass in a given space Mass per unit volume
You can compare the densities of two minerals by lifting two samples that are the same size and seeing which is heavier
Calculate density by taking mass divided by volume
Depends on the kinds of atoms in a mineral and how closely they are packed.
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14. Hardness Measure of the ability to resist scratching
Determined by the strength of the bonds between atoms
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15. Mohs Hardness Scale Standard scale for mineral hardness
To test an unknown mineral you must determine the hardest mineral on the scale it can scratch.
If neither of two minerals scratches the other, they have the same hardness
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16. Crystal Structure Six basic shapes
A certain mineral always has the same basic shape
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17. Cleavage
Tendency to split along specific planes of weakness to form smooth, flat surfaces
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18. Fracture
Tendency to break unevenly into pieces that have curved or irregular surfaces
Described by how it looks when it breaks
Shell-shaped fracture
Hackly fracture (jagged points)
Earthy fracture (crumbly)
Uneven fracture (rough surface)
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19. Special properties
Fluorescence – the ability to glow under ultraviolet light
Phosphorescence – the ability to keep glowing after the ultraviolet light is turned off
Chemical reactivity
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20. Special properties
Asterism – a six-sided star appears in reflected light
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21. Special properties Double refraction Magnetism Radioactivity
Light bending through the mineral produces a double image
Magnetism
Radioactivity
Unstable
Decay over time releasing particles and energy
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22. Discuss Name eight properties that are used to identify minerals
Compare and contrast fracture and cleavage.
Graphite is made of carbon atoms arranged in thin sheets. The sheets are weakly held together. Predict whether graphite will break apart with fracture or cleavage. Explain.
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23. Crystallization
How atoms in a crystal structure get arranged in that structure
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24. Minerals from magma and lava
Magma – molten rock beneath Earth’s surface
Lava – what magma becomes when it reaches the surface
Both form crystals as they cool and solidify
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25. Cooling rates Magma far underground cools slowly
Large crystals, especially if undisturbed
Lava and magma close to the surface cool more quickly
Smaller crystals
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26. Minerals from solutions
Solution – one substance dissolved in another
Minerals dissolved in water
Crystallize when they leave the solution
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27. Evaporation Minerals formed at the edges of bodies of water
Minerals formed as ancient seas evaporated
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28. Geode Rounded hollow rock that is lined with mineral crystals
Formed when solutions of minerals seep into the rock through a crack and then the water evaporates
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29. Hot water solutions Hot water dissolves minerals
The solution flows through cracks in other rocks
As the water cools, crystallization occurs
A vein is formed
Narrow channel or slab of a mineral that is different from the surrounding rock
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30. Discuss What is crystallization?
What factor affects the size of crystals that form as magma cools?
What is a solution?
What are two ways in which minerals can form from a solution?
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31. Gemstones Hard, colorful minerals with brilliant or glassy luster
Valuable minerals
Once polished, called gems
Used for decoration, mechanical parts, grinding and polishing
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32. Metals Not as hard as gemstones
Can be made into wires, thin sheets, hammered, and molded without breaking
Conduct heat and electricity well
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33. Other uses Medicines Fertilizers Talc – baby powder
Gypsum – sheetrock, cement, stucco
Calcite – optical instruments
Quartz – glass, watches, electronics
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34. Ore Rock containing minerals to be mined and sold
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35. Producing metals from minerals
Prospecting – searching for ore
Can use magnetic field for iron, nickel, and cobalt
Mining – getting ore out of ground
Strip mines, pit mines, shaft mines
Smelting – getting metals out of ore
Use density differences to separate
Additional processing
Remove impurities
Make alloys
Solid mixtures of a metal and another element
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36. Discuss What are gemstones? Why are they valuable? What is an ore?
What properties of metal make them useful to humans?
If you were making a machine with lots of small, moving parts that must run constantly, would you make it out of metal or gemstones? Explain.
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