1. Minerals

2. Minerals What is a mineral? What is a rock? Naturally occurring
Crystalline solid
Inorganic
Specific chemical composition
Definite structure
What is a rock?
Composed of one or more minerals

3. Mineral Formation Minerals form from: Cooling magma
Precipitation from water

4. Minerals There are 4500 known minerals
~200 are common
~24 form the majority of rocks
Minerals form under specific heat and pressure conditions
Minerals are used to classify and interpret rocks

5. Properties of Minerals
Seven important characteristics for identifying minerals
Luster
Color (sometimes ambiguous)
Streak
Hardness
Crystal habit
Breakage (Fracture or Cleavage)
Specific Gravity

6. Properties of Matter – Crystal Habit
The external shape
Mineral crystals occur in various shapes and sizes
Shape is determined by the arrangements of the atoms, molecules or ions that make up the crystal and how they are joined

8. Properties of Minerals --Hardness
Measure of resistance to scratching
Hard mineral = very resistant to scratching
Measured on Moh’s hardness scale

9. Properties of Minerals -- Color
NOT always a good diagnostic property – can be misleading
Most minerals have a wide range of colors
Example: Quartz
Color is the result of impurities
A few minerals DO have characteristic colors
Ex. Olivine is always green

10. Properties of Minerals – Streak
The color of powdered mineral
COLOR may vary, but streak is usually the same
Hematite always has a red streak (whether it has an earthy or metallic luster)

11. Properties of Minerals -- Luster
The way light reflects off surface
Metallic
Nonmetallic
Earthy
Glassy
Pearly
Greasy

12. Properties of Minerals – Specific Gravity
Ratio of mineral mass to mass of an equal volume of water
How HEAVY does the mineral feel?
Galena is a heavy mineral

13. Properties of Minerals – Breakage
Cleavage: Break along zones of weakness in crystal lattice
Tendency of a mineral to break along planes of weak bonds
Creates smooth, parallel surfaces

14. Properties of Minerals -- Breakage
Fracture: uneven break when no weak zones exist
Mineral has strong bonds in all directions
Breaks along uneven, irregular surfaces OR
Breaks along curved, conchoidal surface

15. Special Properties Magnetism Taste Reaction to HCl Fluorescence
Magnetite
Taste
Halite tastes salty
Reaction to HCl
Calcite reacts to HCl
Fluorescence
Fluorite, Calcite

16. Economic Minerals Ores
A mineral that contains a valuable substance that can be mined at a profit
Classification can change is the mineral’s supply and demand lowers (may no longer be considered an ore)
Example: iron found in the mineral hematite

17. Economic Minerals Gemstones
Gemstones are minerals that are valuable due to their rarity and beauty
Pure, Very little defects
Rare
Transparent
Even coloration
Hardness >7 (not easily scratched)

18. Gemstones Sapphires and rubies are both corundum (Al2O3)
Sapphires blue are due to titanium and iron
Rubies are red due to chromium
Because of their rareness, rubies and emeralds are more valuable than diamonds