Download Introduction to Minerals

Introduction to Minerals
A little bit about Earth
•As far as we know, no other planet in the solar system has the
unique combination of having all three forms of water.
•Earth has a surface that is covered with liquid water, has
water vapor in the atmosphere, and frozen water on the
land.
•Earth also had solid material making up the surface of the
planet. This is going to be our next unit: Rocks, Minerals and
the interaction of Earth with water.
Earth’s Molten Stage
• During the early formation of the Earth, it
was molten
• During this stage the denser elements, such
as iron and nickel, sank to the deeper
interior of the Earth.
• As the Earth cooled, a thin layer of less
dense materials on the surface formed the
crust.
Earth’s Crust Chemical
Composition
• 8 major elements make up 98.6% of the crust-for simplicity you
need to know two of them, Oxygen and Silicon
• These 8 elements make up the solid materials of the Earth’s crust
and can form minerals and rocks
• A mineral is
1.
2.
3.
4.
5.
a solid,
inorganic
naturally occurring material
that has both a known chemical composition
and a crystalline structure that is unique to that mineral
• A rock is a solid, combination of one or more minerals
• THEREFORE: minerals make up rocks
Common
Materials of
Earth
Details on Minerals
1. Crystal Structures
a. A crystal is a structural unit (pattern) that is repeated in
three dimensions.
2. Density – ratio of the mass of a mineral to its volume.
a.Specific gravity – ratio of mineral density to the
density of water
b. Density Depends on:
Kind of atoms which make up the mineral
How the atoms are arranged in the crystal
This is the basic structural unit of a crystal of sodium chloride,
the mineral halite.
The structural unit for a crystal of table salt, sodium chloride,
is cubic, as you can see in the individual grains.
These quartz crystals are hexagonal prisms.
Details on Minerals
3. Color
A visual measure. Not very useful for identification as color of
minerals vary.
4. Streak
This is the color of the mineral when it is finely powdered. We
measure this by rubbing it across a piece of ceramic tile, leaving a
fine powder of the mineral on the tile.
5. Hardness
Resistance of the material to being scratched. Measured using the
Mohs hardness scale, which compares the hardness of the mineral to
10 reference minerals.
(A)Gypsum, with a hardness of 2, is easily scratched by a fingernail. (B)
Quartz, with a hardness of 7, is so hard that even a metal file will not
scratch it.
Details on Minerals
6. Cleavage
The tendency of mineral to break along smooth, predicable planes .
Depends upon areas of weakness in the crystal structure.
A. Fracture
The broken surface is irregular and not in a flat plane.
Resource:
http://academic.brooklyn.cuny.edu/geology/grocha/mineral/cleavage.
html
Details on Minerals
7. Luster
Surface sheen (the look). Could be:
Metallic – like metal
WaxyPearly – like pearl (shiny, but not see-through)
Vitreous – glasslike
Earthy-
How Minerals Form
In general, minerals can form in two ways: through cooling
of melted materials, and through materials dissolved in
water.
 Minerals can form as hot magma cools deep inside the
crust, or as lava hardens on the surface.
 When water evaporates it leaves behind residue that
forms mineral crystals.
Mineral-Forming Processes-Cooling
Magma: Molten material under the Earth’s surface from which
minerals are formed
VS
Lava: Magma that is forced to the surface of Earth
Influences on the mineral forming process:
1. Temperature
2. Pressure
3. Time
4. Availability and concentration of ions that are in solution
• Bowen’s Reaction Series
•
Arranges the minerals by what temperature
they form at.
•The size of these crystals (the minerals)
depends on several factors.
•The rate at which magma cools, the amount
of gas magma contains, and the chemical
composition of magma all affect crystal size.
Minerals at the top of the series (olivine, augite, and calciumrich plagioclase) crystallize at higher temperatures, leaving the
magma enriched in silica. Later, the leftover magma cools and
less dense minerals (orthoclase feldspar, quartz, and white
mica) crystallize. So the temperature of the magma
determines the minerals it will turn into.
•Slow cooling leads to the formation of
minerals with large crystals.
•If the crystals remain undisturbed while
cooling deep below the surface, they grow
according to a regular pattern.
•On the surface, lava loses heat energy
much faster than magma that hardens deep
below ground.
•With rapid cooling, there is no time for
magma to form large crystals.
Intro to Minerals Movie
https://www.youtube.com/watch?v=8a7p1NFn64s