1. Minerals
Chapter 3

2. What is a Mineral? Mineral Characteristics Naturally occurring
Inorganic
Solid
Definite chemical composition
Either elements or compounds
Have orderly arrangements of atoms
Crystalline/Set atomic pattern

3. The Structure of Minerals
Crystals
Solids in which the atoms are arranged in orderly, repeating patterns.
Minerals are classified into six major crystal systems according to their crystal structures:
Hexagonal
Cubic
Tetragonal
Orthorhombic
Monoclinic
Triclinic

4. The Structure of Minerals
Formation of Crystals:
From the cooling and solidification of magma
The type and amounts of elements present in the magma partly determine which minerals will form.
How rapidly the magma cools determines the size of the crystals.
Slow – large
Fast – little
From the evaporation of a solution or the supersaturating of a solution

5. Mineral Compositions and Groups
Mineral Classification
2 Main Groups:
Silicates
Minerals that contain silicon and oxygen
Contain most of the common rock-forming minerals
Nonsilicates
Do not contain silicon

6. Mineral Compositions and Groups
Mineral Amounts:
About 4,000 different mineral are found on Earth.
Only a few dozen of these minerals are common.
90 elements occur naturally in the crust of the Earth.
~98% of the crust is made of only eight elements.
Silicon and Oxygen are two of the most abundant elements found in Earth’s crust.

7. Identification of Minerals
Hardness
A measure of how easily a mineral can be scratched
Measured on a scale of 1 to 10 called the Mohs Scale.
10 = hardest, diamond
1 = softest, talc
Iron nail = 4.5
Fingernail = 2.5

8. Identification of Minerals
Luster
The way a mineral reflects light.
Metallic or nonmetallic

9. Identification of Minerals
Specific Gravity
Ratio of the weight of the mineral with the weight of an equal volume of water.
Specific gravity of minerals can be roughly relatively tested using heft.

10. Identification of Minerals
Streak
Color of a mineral in a powder form
Found by rubbing the mineral across a porcelain streak plate

11. Identification of Minerals
Cleavage
Mineral breaks along smooth, flat surfaces
Due to the atomic arrangement of the mineral

12. Identification of Minerals
Fracture
Fracture
Mineral breaks along rough, uneven, or jagged surfaces.

13. Identification of Minerals
Color and Appearance
Color and Appearance
Highly unreliable.

14. Identification of Minerals
Other Properties
Other properties
Magnetic
Optics
Chemical reactions

15. Gems Properties of Gems
Gemstones are highly prized minerals because they are rare and beautiful.
Most gems are special varieties of a particular mineral.
Clearer, brighter, or more colorful
Have a slightly different chemical formula:
Amethysts are quartz with a trace amount of iron.
Have a better crystal structure.

16. Gems Important Gems Cullinan Diamond Hope Diamond
Largest uncut diamond discovered
Found in South Africa in 1905
3, carats (621 g)
Cut into 9 main stones and 96 smaller stones
Largest of these, the Great Star of Africa ( carats) is part of the British crown jewels.
Hope Diamond
Purchased by Henry Philip Hope around 1830.
45.52 carats (9 g)
All Hope’s family plus a later owner suffered misfortune.
Currently on display in the Smithsonian.

17. Gems Useful Gems Diamonds Rubies Quartz
Used as industrial abrasives and cutting tools
Rubies
Produce certain types of laser light
Quartz
Used in timepieces and electronics

18. Useful Elements in Minerals
Ores
A mineral or rock that contains a useful substance that can be mined at a profit
Examples:
Iron is found in the ores hematite and magnetite
Aluminum is found in the ore bauxite

19. Useful Elements in Minerals
Extracting Elements
Refining
Wanted element is separated from unwanted materials.
Smelting
The substance is melted to separate it from any remaining unwanted materials.

20. Useful Elements in Minerals
Vein Minerals
Occur when dissolved metallic elements travel in fluid form through weaknesses in rock and form mineral deposits.

21. Useful Elements in Minerals
Titanium
Found in ilmenite and rutile.
Lightweight and durable
Used in auto body parts, aircraft, eyeglasses, etc.