“Minerals” Notes
Mineral definition: is a naturally occurring, nonliving solid, with a definite structure and composition.
 Over 3000 different types worldwide.
 All share 5 characteristics:
1. Formed by natural processes
2. Inorganic
3. All are solid
4. Every mineral is an element or compound with a chemical composition unique to that mineral.
5. They all are arranged in a pattern repeated over and over again.
Structure of Minerals:
A crystal is a solid in which the atoms are arranged in repeating patterns.
All minerals are crystals, but all do not have smooth surfaces and sharp edges.
 Ex. Quartz has a hexagonal crystal shape.
6 Major Crystal Systems:
1. Cubic
Halite like rock salt and pyrite
2. Tetragonal
Wulfenite
3. Hexagonal
Quartz and Corundum
4. Orthorhombic
Topaz
5. Monoclinic
Gypsum
6. Triclinic
Plagioclase
How are minerals formed?
2 ways
From the cooling of hot melted rock, called magma, inside Earth.
 As magma cools, its atoms form a crystal structure and it becomes a mineral. It
depends on the elements present in the magma to what mineral forms.
 If cooling occurs slowly large crystals form
 If air or water comes in contact with material as it reaches the Earth’s surface
the material cools quickly and forms small crystals.
Minerals from solution
 If little or no space is available for crystals to grow the crystals will be too tiny
to see when formed from solution. When room is available large crystals form.
 If a solution becomes supersaturated or overfilled, with another substance,
mineral crystals can begin to precipitate, or drop out of solution.
 They can also dissolve in a supersaturated solution by evaporation. In this case,
the elements left behind can arrange in crystal formation.
Mineral Groups/Composition:
1.
Native element (50)
Free uncombined elements
Some are valuable
o Ex. Gold, Silver
2.
Silicates (Over 500)
Make up roughly 96% of the minerals found in Earth’s crust.
Are metallic elements combined with either single or linked Silicon (Si-O) tetrahedra
o Ex. Hornblende and Grossular Garnet
Halides (100)
Have halogens: F, Cl, Br, I
Combine with metallic atoms and halogen
3.
4.
Sulfides (300)
S and Metallic combined or S and semimetallic
o Ex. Pyrite (Fools Gold) & Realgar
OR
o One or more metallic elements combined with sulfate (SO4)-2 radical
 Ex. Gypsum
5. Oxides and Hydroxides (Over 250)
Oxides have 1 or 2 metallic elements
OR
combined with H2O and hydroxyl-> hydroxide
o Examples: Hematite, Magnetite, and Uraninite (valuable because it is a major
source of uranium
6. Carbonates (200)
One or more metallic elements combined with a Carbonate radical (CO3)-2
o Ex. Calcite
7. Phosphates
Brightly Colored
One or more combined with (PO4)-3
o Ex. Arsenates and Vanadates
Physical Properties
1. Color is one of the most noticeable physical characteristic of a mineral.
Sometimes due to a trace amount of an element.
Least reliable clue for identification.
2. Luster: How light is reflected from a mineral's surface.
Metallic shines luster
OR
nonmetallic dull luster
3. Texture describes how a mineral feels to the touch.
Mineral are softer than unglazed porcelain tile, so a mineral will leave a streak on the tile, where as
minerals harder than the tile will scratch it.
The hardness of a mineral is related to the crystal structure and the type of atomic bond in the mineral.
4. Streak: Is the color of the mineral when it is broken up and powdered.
Ex. Gold has a yellow streak while pyrite (Fool’s Gold) has a greenish-black streak.
Ex. Graphite is used in pencil lead because it is soft enough to leave a streak on paper.
5. Hardness: A measure of how easily a mineral can be scratched.
A German scientist named Friedrich Mohs developed the Mohs' Scale of Hardness (1-10) With
1 being the softest and 10 being the hardest.
6. Cleavage and Fracture: The way a mineral breaks.
Smooth, flat surface break: Cleavage
 Ex. Mica has perfect cleavage.
Rough or jagged edges: Fracture
 Ex. Quartz
7. Density and Specific Gravity:
D=Mass/Volume
Sp.G= Ratio of the weight of a substance to the weight of an equal volume of water at 4oC.
Special Properties
8. Magnetic
Ex. Magnetite
9. Using HCl: For fizz test
Ex. Calcite fizzes
10. Smell/Odor
Ex. Sphalerite produces a distinctive rotten-egg odor when rubbed vigorously across a streak
plate.
o In the Sulfide mineral group
Uses of Minerals
1. Ores-Contain a useful substance that can be mined at a profit.
o To be a true ore the value on the market must be greater than the cost of extraction.
Ilmenite and rutile
o Titanium: Durable, lightweight metal derived from minerals such as ilmenite or
rutile.
 Used in automobile body parts, aircraft, wheelchairs used for racing, hip
replacement parts and other artificial body parts (nontoxic)
The original source of anything made with iron is the mineral hematite.
o Contains 70% iron by weight
Aluminum is found in bauxite ore.
2. Gems- Highly prized minerals that are rare and beautiful.
Diamonds and rubies
3. Asbestos: 2 forms
Asbestos materials do not burn easily and do not conduct heat or electricity very well.
o Floats around in the air when fibers break loose and can cause lung cancer.
 Chysotile: Serpentine group of minerals that is used for insulation and fire
protection
 Fibrous and soluble
 Crocidolite: Amphibole group of minerals used for insulation and fire
protection
 Long, thin, straight, and very penetrating fibers.

Tends to remain embedded in human tissue.
4. Paint pigments:
Ochre: yellow clay that contains Fe
Sienna: Dark yellow clay that contains Fe and Mn, that turns brown (burnt sienna) when
roasted in the oven.
White pigments: Calcium, Zinc, Titanium, or Lead