Mineralogy
The study of minerals and their properties
Ways of Identifying Minerals
Some properties can be determined by looking at the mineral with the naked eye and simple physical tests.
Others need chemical tests.
Identification by Inspection
Luster
Luster is the way the mineral shines.
Can it be metallic, nonmetallic or both?
Galena and Pyrite are two examples.
a mineral that doesn’t shine like a metal is a nonmetallic luster.
Crystal Shape
Recall the 6 different crystal shapes!
Color
Most obvious test!
Simple Tests
The Streak Test
Rub the specimen on unglazed white tile, the resulting color can be used to identify the mineral.
Many times the streak powder is not the same as the color of the mineral.
Hematite is brown, red, or silver.
However its streak powder is reddish-brown.
Cleavage
Cleavage is the mineral’s tendency to split easily.
Fracture is the tendency to have a shell-like split
Hardness
Hardness is the resistance to being scratched.
Friedrich Mohs devised a hardness scale.
Moh chose 10 known minerals and gave them numbers between 1-10.
Hardness is not brittleness!!!
You should know the hardness scale!!!
An easy way to remember it is to remember the following saying:
The girl could flirt and flirt quickly though Connie didn't.
This stands for: Talc Gypsum Calcite Fluorite Apatite Feldspar Quartz Topaz Corundum Diamond
Specific Gravity
Specific gravity is the ratio of the weight of a mineral to the weight of an equal volume of water.
In other words, the specific gravity of a mineral tells you how many times as dense as water the mineral is.
KNOW THE EQUATION FOR SPECIFIC GRAVITY!
The Acid Test
Calcite is the principle mineral in limestone and marble.
By placing a drop of weak HCl on the calcite, the acid fizzes.
The bubbles are carbon dioxide gas.
The Magnetic Test
Some minerals are magnetic like Magnetite.
The Fluorescence Test
Some minerals fluoresce under the black light.
The Taste Test
Halite can be identified with its taste.
The Radioactive Test
Some minerals give off subatomic particles that will activate the Geiger counter.
Double Refraction Test
Light rays shine through transparent specimens.
Descriptions of Rock Forming Minerals
Silicate Minerals
They are made up of silica tetrahedrons combined in various structures.
Recall from class what a silica tetrahedron looks like.
SiO4 (-4)
Common examples
Feldspar
Quartz
Mica
Three types of silicate minerals
1) Amphiboles
Silicate minerals that form long, needle-like crystals.
Example - Hornblende
2) Pyroxenes
Silicate minerals that form shorter, stouter crystals.
Example - Augite
3) Ferromagnesian silicates
Include any dark silicate mineral containing iron and magnesium.
Hornblende, Augite, and olivine are examples.
Carbonate Minerals
Calcite and Dolomite are the two most important carbonate minerals.
Iron oxides and Iron sulfides
Iron oxides contain large amounts of iron combined with oxygen.
Hematite and Magnetite are examples
Iron sulfides contain large amounts of iron combined with sulfur.
Pyrite is an example
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