1. Minerals

2. Minerals
Natural, usually inorganic solid that has a characteristic chemical composition, an orderly internal structure, and a characteristic set of physical properties.

3. Is it a Mineral? Is it organic? Does it occur naturally?
Is it a crystalline solid?
Consistent chemical composition?
Must answer yes to all 4 questions for it to be a mineral

4. 10 Most common minerals Quartz Calcite Orthoclase Dolomite
Plagioclase Halite
Muscovite Gypsum
Biotite Ferromagnesian
Calcite Minerals
These make up 90% of Earth’s mass

5. Mineral Groups Silicates 96% of Earth’s crust Contains Si and O
Can have other elements also
Feldspar – Orthoclase if K, Plagioclase if Na or Ca
Ferromagnesian minerals – rich in Fe

6. Mineral Groups Nonsilicate Minerals Do not contain Si and O Six groups
Can contain one or the other, but not both
Six groups
Carbonates Native elements
Halides Oxides
Sulfates Sulfides

7. Crystalline Structure
Crystal – atoms, ions, or molecules are arranged in a regular, repeating pattern
Silicate crystal structure
Silicon – oxygen tetrahedron
1 Si with 4 O’s around it
Basic building block of silicates
Can be connected 6 different ways

8. Crystalline Structure
Nonsilicate crystals
Diverse chemical composition leads to variety of crystal structures
Cubes, hexagonal prisms…
Crystal structure influences physical properties
Native elements are dense due to compact crystal structure

9. Silicate Tetrahedron

10. Physical Properties of Minerals
Mineralogist
Examine, analyze, and classify minerals
Result from chemical composition and crystal structure
Can be useful in identifying minerals

11. Physical Properties Color Not reliable for ID purposes
Small amount of impurities can affect color
Weathered surfaces may hide color
Only look at fresh surfaces

12. Color

13. Physical Properties Streak Color of mineral in powder form
Streak plate – unglazed ceramic tile
Streak color may differ from mineral color
Metallic minerals – darker streak
Nonmetallic minerals – lighter streak

14. Streak

15. Physical Properties Luster Light reflected from mineral’s surface
Metallic luster – shiny surface
Nonmetallic luster
Glassy
Waxy
Pearly
Brilliant
Dull / Earthy

16. Metallic Luster

17. Glassy Luster Quartz

18. Waxy Luster Variscite

19. Pearly Luster Talc

20. Brilliant Luster Diamond

21. Dull / Earthy Luster Psilomelane

22. Physical Properties Cleavage / Fracture Cleavage Fracture
splitting along specific lines of weakness
Forms smooth, flat surfaces
Fracture
Break unevenly into pieces
Forms curved, irregular surfaces
Conchoidal fractures – curved surface

23. Cleavage - Calcite

24. Fracture Conchoidal

25. Fracture Irregular

26. Physical Properties Hardness Ability to resist scratching
Mohs Hardness Scale
Scale of 1 to 10
1 = Talc 10 = Diamond
Glass is about a 5

27. Mohs Hardness Scale

28. Physical Properties Crystal Shape Density 6 Basic shapes
Certain minerals always form crystals with the same shape
Density
Ratio of mass to volume
Can help identify minerals

29. Crystal Shapes

30. Physical Properties Fluorescence and phosphorescence
Chatoyancy and asterism
Double refraction
Magnetism
Radioactivity

31. Double Refraction