Minerals

Properties

&

Special Properties

Earth’s CrustEarth’s Crust

• Made of Rock• Rock is made of minerals (and other

stuff)• Minerals …

– are naturally made.– are inorganic (non-living) – are solid.– have a definite chemical composition

which give it definite crystal shape

Earth’s CrustEarth’s Crust

• Most abundant elements in Earth’s crust– #1 – oxygen– #2 – silicon– #3 – Aluminum – #4 – Iron– #5 – Calcium

Mineral FamiliesMineral Families Silicates – Most Abundant

Must contain silicon and oxygen SiO2 (quartz)

Carbonates – most often used in building industry (cement, concrete, etc.)Must contain carbon and oxygen CaCO3 (calcite)

HalidesMust contain Fluorine, Chlorine, Iodine or BromineCaFl2 (fluorite)

SulfatesMust contain sulfur and oxygenBaSO4 (barite)

Mineral Families (cont.)Mineral Families (cont.)Sulfides

Must contain sulfur and a metal (no oxygen)ZnS2 (pyrite)

Oxides (used to make steel, etc.)must contain a metal and oxygenFe3O4 (magnetite)

Native Elements One single element Au (Gold) C (Diamond)C (Graphite)

Mineral PropertiesMineral Properties

• Color• Crystal Structure• Hardness• Heft/Specific

Gravity (density compared to water)

• Luster• Break Pattern

(Cleavage or Fracture)

• Streak

Click below for video clip

Property: Color

• Not reliable because some minerals have impurities that make one mineral different colors– Example: Quartz

• Several minerals can also share the same color– Example: Quartz, Calcite, Halite can all be

clear

Milky Quartz

Rosie Quartz

Smokey Quartz

Amethyst

Crystal StructureCrystal Structure• A repeating pattern of atoms, ions, or molecules

that is present throughout a mineral.• Examples – cubic, hexagonal, triclinic

HardnessHardness

• A A mineral’s mineral’s resistance to resistance to being scratched being scratched or mechanically or mechanically broken downbroken down

• Use Mohs Use Mohs Scale.Scale.

Moh’s Scale of HardnessHardness Minerals/Gemstones Test

1 Talc, SulpherScratched

w/fingernail

2 Gypsum, Amber (2-3)Scratched

w/fingernail

3Calcite, Coral (3-4),

Pearl (3-4), Malachite (3.5-4)

Scratched w/copper penny

4 Fluorite, RhodochrositeScratched w/

knife blade easily

5Apatite, Lapis (5-6),

Turquoise (5-6), Opal (5.5-6)

Scratched w/knife blade

6Feldspars, Moonstone,

Tanzanite (6.5-7), Peridot (6.5-7)

Scratched w/steel file

7Quartz, Tourmaline (7-

7.5), Garnet (7-7.5), Beryl (7.5-8)

Scratches glass

8Topaz, Alexandrite (8-

8.5)Scratches

glass

9 CorundumScratches

glass

10 DiamondScratches

glass

Hardness of Graphite and Diamond

• Graphite (fragile and soft) and diamond (hardest known substance on Earth) are both made of carbon.

• Why are they so different?– http://www.edinformatics.com/interactive_molecules/graphite.htm

– Internal bonding arrangements of the carbon atoms.

Heft/Specific Gravity

• Density of a mineral compared to density of water (Water’s density is 1 g/mL)

• Or - way of determining the density of a mineral by “feeling” how heavy it feels for its size– Example – the heft of mica is less than

magnetite (mica feels “lighter” than magnetite when they are the same size)

LusterLuster

• How a mineral reflects light – is it shiny or dull…is it glassy or pearly…is it metallic or non-metallic?

Break Break Pattern – Pattern –

Cleavage & Cleavage & FractureFracture• Cleavage –

when broken, the mineral has smooth flat surfaces

Break Pattern – Break Pattern – Cleavage & Cleavage &

FractureFracture• Fracture – when broken, the mineral has jagged, uneven surfaces

StreakStreak• The color of a

mineral in powdered form – use an unglazed porcelain plate.

• More reliable than the color property – the streak for each

type of quartz is the same (clear/white)

Special PropertiesSpecial Properties

• Smell – sulfur smells like rotten eggs

Special PropertiesSpecial Properties• Taste – halite

tastes salty (some minerals are poisonous so CAREFUL with this one!

• Fluorescence – fluorite glows under UV light

Special PropertiesSpecial Properties• Magnetism – magnetite attracts

metal

• Double Refraction (bends light) – calcite

Special PropertiesSpecial Properties• Reacts with acid –

calcite bubbles/fizzes with acid

• Feel – talc and graphite feel greasy or slick