inside the restless earth ch. 1 minerals of the earth’s crust
TRANSCRIPT
Mineral Structure
• element - a substance that cannot be separated or broken down into simpler substances by chemical means.
• Each element is made of only one kind of atom.
The element sodium.
Mineral Structure
• compound - a substance made of two or more elements that have been chemically combined.
• Na + Cl = NaCl
The compound halite.
Mineral Structure
• crystal - a solid whose atoms, ions, or molecules are arranged in a definite repeating pattern.
• The arrangement of atoms
is determined by the kinds
of atoms.
Amethyst.
Two Groups of Minerals
1. Silicate minerals - minerals that contain a combination of silicon, oxygen, and often one or more metals.
- Make up > 90% of Earth’s crust
Common Silicate Minerals
Feldspar
KAlSi3O8
Quartz
Silicon Dioxide
SiO2
Mica
Biotite
K(Mg, Fe)3AlSi3O10(F, OH)2
Two Groups of Minerals
2. Nonsilicate minerals - minerals that do not contain compounds of silicon and oxygen.
Gypsum
Classes of Nonsilicate Minerals
Oxides - form when an element (such as aluminum or iron) combines chemically w/ oxygen.
CorundumAl2O3
Aluminum oxide
Classes of Nonsilicate Minerals
Carbonates - contain combinations of carbon and oxygen in their chemical structure.
CalciteCaCO3
Classes of Nonsilicate Minerals
Sulfates - contain sulfur and oxygen, SO4.
Gypsum
Calcium Sulfate Dihydrate
CaSO4·2H2O
Classes of Nonsilicate Minerals
Halides - form when:
flourine, chlorine, iodine, or bromine
combine with
sodium, potassium, or calcium
FlouriteCalcium Fluoride
CaF2
Classes of Nonsilicate Minerals
Sulfides - contain one or more elements (such as lead, iron, or nickel) combined with sulfur.
GalenaLead Sulfide
PbS
Section 2: Identifying Minerals
Color
- the same mineral can come in a variety of colors
- usually not the best way to identify a mineral
Section 2: Identifying Minerals
Luster - the way a surface reflects light.
1. Metallic - bright, reflective
Gold
Section 2: Identifying Minerals
Streak - the color of a mineral in powdered form.
- the mineral is rubbed
against a streak plate
- streak is not affected
by air or water
- more reliable than
mineral color
Cleavage and Fracture
Cleavage - the tendency of some minerals to break along smooth, flat surfaces.
Cleavage and Fracture
Fracture - the tendency of some minerals to break unevenly along curved or irregular surfaces.
Conchoidal fracture
Density
Density - measure of how much matter is in a given amount of space. d = m / v
gold = 19 g/cm3
Specific gravity - the ratio of an object’s density to the density of water.
gold = 19
Special Properties
Chemical reaction - look for bubbling when combined with an acid.
CaCO3 + 2HCl = CO2 + H2O + CaCl2
calcite hydrochloric acid
Special Properties
Optical properties - such as double refraction.
Same sample of calcite, but it’s rotated.
Special Properties
TasteNever taste a mineral without the
teacher’s permission.
Borax tastes sweet.
Halite tastes salty.
How Do Minerals Form?
LimestonesAs water runs along the surface of the Earth and
seeps through the ground, it dissolves minerals and
carries them to large
bodies of water, where
they crystallize on the
bottom.
How Do Minerals Form?
Evaporating Salt WaterMinerals such as halite crystallize when salt water
evaporates.
How Do Minerals Form?
Metamorphic RocksChanges in pressure, temperature, or chemical
makeup can form new minerals such as garnet.
How Do Minerals Form?
Hot-Water SolutionsMagma heats groundwater, which now more easily
reacts with and dissolves minerals. The minerals
then crystallize out of
the solution. This
vein of gold was
formed this way.
How Do Minerals Form?
PegmatitesMagma can move upward into these teardrop-shaped
bodies. Pictured here is a sample of tourmaline from
a pegmatite.
Mining
Subsurface MiningUsed to remove minerals
located too deep within the
Earth to be surface mined.
Responsible Mining
Potential mining problems:- Can disturb or destroy habitats
- Waste products may pollute surface water and
groundwater
Responsible Mining
Potential mining problems:- Can disturb or destroy habitats
- Waste products may pollute surface water and
groundwater
Solutions:- Reclamation: return mined land to its original state
- Reduce need for minerals by recycling
The Use of Minerals
Metallic Minerals- Have shiny surfaces
- Do not let light pass
through them
- Good conductors of heat
and electricity
The Use of Minerals
Nonmetallic Minerals- Have shiny or
dull surfaces
- May let light
pass through
them
- Good insulators
of electricity