Mineral Characteristics
• I. Mineral Characteristics:
A. Mineral - is a naturally occurring, inorganic solid with a
definite structure and composition.
B. There are more than 4000 minerals found on earth.
C. All minerals share five characteristics.
1. All minerals are formed by one of three natural processes.
A.) Formed from cooled magma.
- Magma - hot melted rock under earth’s surface.
B.) Form from minerals dissolved in liquid.
- After the water evaporates the mineral stays
behind & dries. This forms the mineral.
C.) New minerals could form from existing minerals.
-They could be transformed by:
-Heat
-Pressure
-Chemical Reaction
-Mineral atoms change without melting, allowing
the atoms to recombine in new ways.
Mineral Characteristics Cont.
2. All minerals are inorganic.
A.) Minerals are not alive, never were, and were not
made up by once living things.
B.) Example: Is coal a mineral? Is Oil a mineral?
Coal and Oil formed from one living things.
3. All minerals are solid and have a definite shape.
A.) Liquids + Gases could never be minerals because
they do not have a definite shape.
4. All minerals have definite chemical compositions.
A.) Some rocks are made of different things.
5. A mineral’s atoms are arranged in a definite pattern, that
repeats over and over again.
Mineral Characteristics Cont.
A.) The repeating pattern of atoms are called crystals.
B.) When magma cools slowly, large crystals form.
C.) When magma cools rapidly, small crystals form.
• II. Mineral Identification:
A. Properties of minerals:
Appearance - you cannot rely on a minerals appearance
alone to tell them apart. Ex. Gold and Pyrite (Fools Gold).
1. Hardness - is how easily a mineral can be scratched.
A.) We can use hardness to identify minerals by using
the Mohs Scale of Hardness.
Questions
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About how many minerals are found on earth?
What are the five characteristics that all minerals
must have?
What are the three ways a mineral can form
naturally?
Why is coal not a mineral?
Can liquids or gases ever be minerals? Why?
“Mineral Identification Cont.”
B.) An object with a hardness of 1 is the softest, and an
object with a hardness of 10 is the hardest mineral.
C.) Objects with the same hardness will scratch each
other.
D.) Which mineral is harder Quartz or Calcite?
2. Luster - Describes how light is reflected from the
mineral’s surface.
A.) Luster will be either metallic or nonmetallic.
B.) Metallic - shines like metal.
C.) Nonmetallic - does not shine like a metal.
D.) Ex. Gold - metallic, Quartz - nonmetallic.
“Mineral Identification Cont.”
3. Color – The appearance of the mineral in reflected light.
What you see to the naked eye.
A.) Usually not enough.
B.) Gold and Pyrite.
4. Streak - is the color of the mineral when it is broken up
and powdered.
A.) When a mineral is rubbed across an object with a
greater hardness a streak of color is sometimes left
behind.
B.) Ex. Gold leaves a yellow streak, and Pyrite leaves a
grayish streak.
“Mineral Identification Cont.”
5. Cleavage - Minerals have cleavage if it can break across
a smooth flat surface.
A.) Ex. A layer cake taken apart in layers is broken with
perfect cleavage.
B.) Halite and Calcite break with perfect cleavage.
6. Fracture - Minerals that break with rough or jagged edges
have fracture.
A.) Grabbing a chunk out of a layer cake would be like
breaking a mineral with fracture.
B.) Quartz has fracture.
“Mineral Identification Cont.”
7. Special Properties - some mineral have unique properties.
Examples:
A.) Calcite fizzes when Hydrochloric Acid (HCl) is put
on it.
B.) Magnetite is attracted to magnets.
C.) Halite dissolves in water.
• III. Uses of Minerals:
A. Gems - a valuable mineral highly prized because they are
rare and beautiful.
1. Most minerals are forms of gems.
“Uses of Minerals”
2. Example: Amethyst is a gem form of Quartz.
3. The gem’s value depends on its rarity, size and cut.
4. The most rare and valuable gems are called Precious
Stones.
5. All other gems are called Semiprecious Stones.
A.) Examples: Amethyst, Turquoise, and Topaz.
B.) Ores - a mineral that contains a useful substance that can be
extracted and used for a profit.
1. Iron can be extracted from Hematite.
2. Aluminum can be extracted from Bauxite.
“Uses of Minerals”
3. The value of an ore depends on its supply ; its demand
and cost of extraction.
4. If it cost raises, or demands fall, a substance may not be
considered an ore.
Removing Iron from an ore
• Iron ores are typically the iron atom bonded with oxygen.
• The metallic iron can be removed from a process called
smelting
– Iron ore is crushed and mixed with limestone and coke (baked
coal)
– Mixture is placed in a blast furnace with extremely hot air to make
the coke easily burn.
– Chemical reactions with the coke changes allow the mixture to
form carbon dioxide gas and molten iron
– Molten iron sinks to the bottom of the furnace as impurities
combine with the limestone to make slag (floating on top).
– Slag is removed and iron is poured out through taps.
Processing of iron
• 98% of iron is used in the production of
steel.
• Steel is an alloy made from mostly iron and
carbon.
– Alloy is a mixture of two or more elements
with at least one being a metal.
Questions
6). Can you rely on a minerals appearance or color alone, in identifying a
mineral? Why?
7). How do you use the Moh’s hardness scale?
8). If you rub two minerals together and both of them are scratched, what
can be said about those two minerals?
9). What is the difference between metallic and nonmetallic?
10). What determines a gemstones value?
11). What determines the value of an ore?