Post on 17-Jan-2018
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Minerals
Mineral - A naturally occurring inorganic solid with specific chemical composition and a definite crystalline structure.
• Materials made in a lab are not minerals.• Materials that are alive or were once alive
are not minerals.• No gas or liquid can be considered a
mineral.• A mineral is a crystal which is arranged in
repeating geometric pattern.
Formation of Minerals(two ways)
1. Minerals are formed from the cooling of magma.
• As magma is forced up to the crust it cools and the atoms begin to interact chemically.
• The rate of cooling determines the size of the mineral.
• The slower the cooling the larger the crystal
2.Minerals Formed From Solution
• Minerals can form from a solution that has become saturated.
• When they reach saturation (supersaturated) they precipitate.
• Secondly, when minerals dissolve in a solution and then the liquid evaporates. Ex. Gypsum and halite
Silicate - tetrahedron
Mineral Shapes
Mineral Groups
• 1. Silicates- Makes up 96% of the minerals found in the Earths crust. Are composed of oxygen and silicon and one or more elements.
• S and O bind in a tetrahedron shape (see fig. page 81)
• Examples of silicates are Feldspar, quartz, and Mica
Feldspar
Mica ex of cleavage
Carbonates• Carbonates- Are minerals composed of one
or more metals and a carbonate (CO3 ).
• Examples , calcite, dolomite, & rhodochrosite, malachite and azurite see p. 83.
Carbonates are found in rocks such as marble and limestone.
carbonates
malachite azurite
Coquina
Limestone
Marble
Oxides• Oxides- Are composed of oxygen and a
metal.• Examples are Hematite (Fe2O3) and
magnetite(Fe3O4)• Uranitite contains uranium which is used to
generate nuclear power.
Final note: Minerals formed in a open space look different from minerals that formed in a closed space, see p. 79
Hemitite
Uraninite• Major source of
uranium used to generate nuclear energy
Magnetite Fe3O4
• Hematite and magnitite are good sources of iron
Other major mineral groups
• Sulfides-pyrite• Sulfates-anhydrite• Halides-halite• Native elements-copper
metal
copper
Mineral Identification
1. Color – The presence of trace or compounds within a mineral.
Ex. Red Jasper Quartz has traces of iron oxides.
Ex. Milky cloudy Quartz could be bubbles of gas or liquid trapped in the mineral.
2. Luster
The way a mineral reflects light.Luster can be described as metallic or
non-metallic.EX. Silver, gold, copper, and galena are
metallic. Other luster descriptions are: Dull,
pearly, waxy, or silky.
3. Texture- Is how a mineral feels to the touch.
Descriptive words used: Smooth, rough, ragged, greasy, soapy, or glassy.
4. Streak Certain minerals leave a streak of color when
run across an unglazed porcelain tile. The streak is not always the same color as the mineral.
Ex. Pyrite is a gold color but leaves a greenish black streak.
No matter how much a mineral is weathered or which color it is the streak is always the same.
Streak can only be used on minerals softer than porcelain.
5. Hardness• Measure how easily a mineral can be
scratched.• Fredrick Moh developed a scale in
which the hardness of a mineral can be compared to the hardness of ten known minerals this is known as Moh’s Scale. See on page 86 Table 4-3.
Moh’s Scale
6. Fracture and cleavage• Atomic arrangement determines how
minerals will break. Minerals break along planes where atomic bonding is weak.
• Ex. Mica is said to have cleavage because it breaks in flat planes.
• Ex. Obsidian breaks with a rough or jagged edge and is said to fracture.
fracture cleavage
7. DensityDensity • Is the atomic mass• Is expressed as ratio of mass divided
by its volume. D=m/V• Geologist use Specific Gravity to
measure Density which is the ratio of weight of a substance to an equal amount of water.
Special Properties• Island spar a type of calcite, causes light to
bend as it passes through the mineral. As you look through it , you will see double images.
• This is known as double refraction, zircon exhibits this special property as well.
• Calcite (CaCO3) also fizzes when it comes in contact with Hydrochloric acid (HCL).
CaCO3 + 2HCL CaCl2 + H2O + CO2
Other special properties…..
• Magnetism ex. Magnetite• Distinctive rotten-egg odor when
streaked on a plate ex. Sphalerite as a result of the
presence of sulfide in the mineral.
Ore
A mineral is an ore if it contains a useful substance that can be mined for a profit.
• Ex. gold, silver, titanium, & aluminum
Gem • Valuable minerals
that are prized for their beauty and rarity.
Ex. ruby, emerald (more valuable than diamonds), diamond, satfire.
Trace elements
• Found in some gems. • Ex. Amethyst contains trace element
which give the gem a lovely purple color.
• Sapphires contain trace amounts of cobalt or titanium.
Mineral Uses
• Computers• Cars
Televisions• Desks• Roads • Medicines
• Building• Jewelry• Beds• Paints• Sports
equipment