1. Introduction to Minerals
Definition, Classification, Identification

2. Introduction to Minerals: Outline
Criteria to “qualify” as a mineral
Formation of minerals (in brief)
Classification of minerals
Identification of minerals

3. Definition of a Mineral
Five Criteria:
Solid
Naturally Occurring
Inorganic
Definite Chemical Composition
Crystal (adj: Crystalline)

4. Definition of a Mineral: Naturally Occurring
If you’re paying attention, this is a NON-EXAMPLE.

5. Definition of a Mineral: Inorganic
If you’re paying attention, this is a NON-EXAMPLE. Sugar is the product of a living thing (i.e., “organic”) and is therefore not a mineral.

6. Definition of a Mineral: Definite Chemical Composition
Example:
“Halite” just is NaCl
There may be slight
impurities.

7. Definition of a Mineral: Crystal Structure
Atoms form an orderly and repeating arrangement

8. Formation of Minerals Must have conditions for good crystal growth!
One: Slow cooling of “magma” – hot, liquid rock material
Two: Slow evaporation of water that has dissolved compounds
Forms an “evaporite” (see next slide)

9. Formation of Minerals: Evaporite Example

10. Classification of Minerals
Classified based on CHEMICAL COMPOSITION
i.e., what they’re made of
there is tolerance or “fudge factor” for some small impurities
The following are MAJOR groups, but not exhaustive!

11. Classification of Minerals: Silicates
Silicates contain silicon and oxygen in the chemical formula
Example: Quartz, SiO2 (the simplest example)

12. Classification of Minerals: Oxides
Oxides contain oxygen in the chemical formula (except when part of another class)
Example: Hematite, Fe2O3

13. Classification of Minerals: Sulfides
Sulfides contain sulfur in the chemical formula (except when part of another class)
Example: Pyrite, FeS2

14. Classification of Minerals: Halides
Halides contain a halogen (Group 17 element) in the chemical formula
Example: Fluorite, CaF2

15. Classification of Minerals: Carbonates
Carbonates contain the polyatomic ion “carbonate” in the chemical formula
i.e., CO3 (which has a 2- charge)
Example: Calcite, CaCO3
Note that this is NOT an oxide.

16. Classification of Minerals: Sulfates
Sulfates contain the polyatomic ion “sulfate” in the chemical formula
i.e., SO4 (which has a 2- charge)
Example: Celestite, SrSO4
Note that this is NOT an oxide NOR a sulfide.

17. Identification of Minerals
Guiding Principles
A single test is never good enough.
Many minerals STRONGLY RESEMBLE other ones.
Even individual samples can be outside the norm.

18. ID of Minerals: Color Test

19. ID of Minerals: Luster Metallic vs. Nonmetallic
glassy, vitreous, dull, etc.

20. ID of Minerals: Scratch Test (Hardness)
Mohs Scale of Hardness
“To scratch, or to be scratched?”
System is just relative rankings (“ordinal”)

21. ID of Minerals: Streak Test

22. ID of Minerals: Crystal Shape

23. ID of Minerals: Breaking Good?
CLEAVAGE
Some minerals break along a flat plane, forming a smooth surface
E.g., “basal
cleavage” is
breaking into
thin sheets

24. ID of Minerals: Breaking Bad?!
FRACTURE
Other minerals break in jagged or curved ways
“conchoidal fracture” -
forms smooth, rounded edges

25. ID of Minerals: Miscellaneous Tests
Taste test?! (DO NOT DO THIS ONE.)
Magnetism test
UV light test (at bottom left)
Optical test (for calcite only, at bottom right)
Carbonate / acid test (see next slide)

26. ID of Minerals: Carbonate / Acid Test
Any carbonate mineral should react with hydrochloric acid:
XCO3 + 2HCl → XCl2 + H2O + CO2

27. Check Yourself Attempt to classify these minerals:
Molybdenite, MoS2
Kyanite, Al2SiO5
Blodite, Na2Mg(SO4)2
Why is color not a good indicator of a mineral’s identity?
What kinds of conditions form good mineral samples?

28. MINERALS