1. Minerals

2. What is a Mineral? Naturally occurring Inorganic Solid
Definite crystalline structure
Definite chemical composition

3. Mineral characteristics
Naturally formed
No substance created in a lab can be a mineral.
examples: plastic, steel, sugar, paper
Inorganic
Not living
Solid
Liquids and gases are not minerals.
examples: water, petroleum, lava, oxygen

4. Mineral characteristics
Characteristic crystalline structure
must have an ordered arrangement of atoms
displays repetitive geometric patterns in 3-D
glass not a mineral (no internal crystalline structure)
Definite chemical composition
must have consistent chemical formula
examples: gold (Au), quartz (SiO2), orthoclase (KAlSi3O8)
basalt (like many other rocks) contains variable ratios of different minerals; thus, has no consistent formula

5. Mineral Structure Crystals: solids with atoms arranged in orderly, repeating patterns.

6. Some crystals form from magma, hot melted rock below the Earth’s surface.

7. When magma cools slowly, crystals are large.

8. When magma cools quickly, crystals are small.

9. Crystals can form from solutions as water evaporates or if too much of a substance is dissolved in water.

10. Minerals are the building blocks of rocks
GRANITE ROCK
Minerals are the building blocks of rocks

11. Mineral Structure Contain one or more elements which are made of atoms
Most made of compounds of several elements (Quartz SiO2)
Mineral composed of one element called native element (Gold Au)
Other minerals broken into groups based on chemical composition
Types of atoms/molecules that make up mineral and arrangement determine shape of mineral

12. Identifying Minerals Six main properties: Special Properties Color
Luster
Streak
Cleavage or Fracture
Hardness
Density/specific gravity
Special Properties

13. Identifying Minerals Color: Most obvious, but often misleading
Many minerals have same/similar color
Different colors may result from impurities
Example:
Quartz

14. Can you remember the definition of a mineral?
Discuss the following!
Can you remember the definition of a mineral?
How many properties can you remember?
Why isn’t color a very good property to identify most minerals?

15. Identifying Minerals Luster:
How a mineral surface reflects light (shines)
Two major types:
Metallic luster
Non-metallic luster
Metallic
example:
Galena
Non-metallic
example:
Orthoclase

16. luster
There are several terms used to describe nonmetallic luster. Examples could be vitreous, like the quartz on the left, or pearly, like the gypsum on the right.

17. Other terms that might be used include greasy, dull, and earthy.
Can you tell which of these has an earthy luster and which has a vitreous luster?
Were you
Right?
Vitreous
Earthy

18. Identifying Minerals Streak:
Streak – color of a mineral in powdered form
(used for metallic minerals)
Obtained by scratching a mineral on a piece of unglazed porcelain.
Example:
Hematite

19. The streak is often not the same color as the mineral.
A minerals color may vary, but the streak rarely will!

20. Identifying Minerals Cleavage vs. Fracture: The way a mineral breaks
Cleavage: tendency of a mineral to break along planes of weakness (smooth)
Minerals that do not exhibit cleavage are said to fracture (uneven)

21. Minerals with cleavage break along smooth, flat surfaces.

22. Physical Properties of Minerals
Cleavage (1 direction):
Example: mica

23. Physical Properties of Minerals
Cleavage (2 directions):
orthoclase
amphibole

24. Physical Properties of Minerals
Cleavage (3 directions):
halite
calcite

25. Physical Properties of Minerals
Cleavage (4 directions):
fluorite

26. Physical Properties of Minerals
Fracture:
minerals that do not exhibit cleavage are said to fracture
minerals with fracture break with uneven, rough, or jagged surfaces

27. Identifying Minerals Hardness: relative scale
How easy it is to scratch a mineral
Mohs Scale of Hardness
relative scale
consists of 10 minerals, ranked 1 (softest) to 10 (hardest)

28. Mohs Scale of Hardness - Copper penny (3.5) - Wire nail (4.5)
Hardest (10) – Diamond
Softest (1) – Talc
Common objects:
- Fingernail (2.5)
- Copper penny (3.5)
- Wire nail (4.5)
- Glass (5.5)
- Streak plate (6.5)

29. Identifying Minerals Specific gravity:
weight of a mineral divided by weight of an equal volume of water
metallic minerals tend to have higher specific gravity than non-metallic minerals
Galena
SG=7.5
Quartz
SG=2.67

30. Specific Gravity/Density=
Density – how much matter is in something (Density=mass/volume)