1. Minerals, Rocks and the Rock Cycle

2. What is a mineral? Occurs naturally Is a solid
Definite chemical composition
Atoms arranged in orderly pattern

3. May Be Elements or Compounds
Gold at Fort Knox
Native Minerals
Form uncombined in nature
Au, Ag, Cu, S, C
Gold, silver, copper, sulfur, diamond
Most are compounds
Form from magma
Form as evaporites
Changed by heat, pressure, or water
Flash: Minerals, Gems and Ores

4. Silicates 90% minerals on Earth Si, O, and 1 or more metallic ions
Most common
Si, O, and 1 or more metallic ions
Si04
Tetrahedron shape

5. How can I tell what this is?
Identifying Minerals
Over 200 known
Can be identified from physical properties
How can I tell what this is?

6. Identification Properties
COLOR
Least useful
Many have similar colors
Other elements may change color
Beryl (emerald)

7. Colors of Quartz

8. Identification Properties
LUSTER
The shine in reflected light
LUSTER TERM
DESCRIPTION
adamantine
very brilliant - as in diamond
resinous
looks like resin or hardened tree sap
vitreous
glassy, but not as shiny as diamond
metallic
looks like metal
silky
has a smooth and fibrous sheen
pearly
smooth and iridescent
greasy
looks like it's coated with oil
earthy
looks like dirt

9. LUSTER
Glassy
Adamantine
Greasy

10. Identification Properties
CRYSTAL SHAPE
Hard to find
Must have room to grow
Crystal Systems
Cubic
Orthorhombic
Tetragonal
Triclinic
Hexagonal
Monoclinic

11. Identification Properties
STREAK
Color of its powder
Does not change
Metallic: as dark as sample
Nonmetallic: white to colorless
Streak Plate ↑

12. Identification Properties
CLEAVAGE
Tendency to split easily or break along flat surfaces
Mica – 1 direction
FRACTURE
Break on uneven surfaces
Conchoidal - obsidian

13. Identification Properties
HARDNESS
Resistance to being scratched
Mohs’ Scale of Hardness

14. Mohs’ Scale of Hardness
1 - Talc – fingernail scratches it easily
2 - Gypsum – fingernail scratches it
3 - Calcite – copper penny just scratches it
4 - Fluorite – steel knife scratches it easily
5 – Apatite – steel knife scratches it
6 – Feldspar – steel knife does not scratch it easily; it scratches window glass

15. Mohs’ Scale of Hardness
7 – Quartz – hardest common mineral; it scratches steel and hard glass easily
8 – Topaz – harder than any common mineral
9 – Corundum – it scratches topaz
10 – Diamond – hardest of all minerals

16. Special Identification Properties
Fluorescence

17. Special Identification Properties
Magnetism
Magnetite

18. Special Identification Properties
Taste
This will quickly identify the mineral halite (salt). If you are new to this process you must use this one with caution, as you never know what the unknown may be.
Often, you may need to resort to this method (until you more fully understand other identifying traits) to differentiate halite from calcite.
If you do taste the sample (especially in a class environment) you should realize that it has been handled by and probably tasted by hundreds of others.

19. Rocks & the Rock Cycle James Hutton – uniformitarianism
“The present is the key to the past”
Geologic processes that happen today happened in the past
Earth’s present physical features were formed by these processes
Flash: Rock Cycle 19:41

21. Igneous Rocks 2 kinds of magma Formed by cooling & hardening of magma
Plutonic – intrusive, forms underground
Volcanic – extrusive, forms on surface
2 kinds of magma
high SiO2%, light colored, thick, slow moving
low SiO2%, dark colored
called mafic

22. Igneous Rocks Grain size and texture depends on how quick cooled
Slow = large crystals
Fast = small crystals

23. Igneous Rocks Grouped based on mineral composition Light = granite
Dark = gabbro

24. Enormous mass of intrusive igneous rock (rock made of once-molten material that has solidified below the earth's surface).
Granite, have steep walls, no visible floors, and extend over thousands of square miles.
Form either as one large mass or many smaller masses at great depths and are exposed only after considerable erosion.
Associated with plate boundaries.

25. Sedimentary Rock Form from sediments hardening into rock
From pieces of other rocks clastic, sandstone, shale
Precipitating out of a solution chemical, limestone, rock salt
From remains of plants & animals organic, coal, limestone

26. Conglomerate
Conglomerate is a sedimentary rock that contains large (greater than two millimeters in diameter) rounded clasts (pieces of rock). The space between the clasts is generally filled with smaller particles and/or a chemical cement that binds the rock together.

27. Sandstone

28. Limestone

29. Shale

30. The Law of Superposition
Sedimentary Rock
Most formed under water, but also in deserts/dunes
Cemented together by SiO2, CaCO3, or FeO
The Law of Superposition

31. Sedimentary Rock
Some contain fossils

32. Sedimentary Rock
Almost all show strata (layers)

33. Sedimentary Rock

34. Some show ripple marks or mud cracks
Sedimentary Rock
Some show ripple marks or mud cracks

35. Metamorphic Rock “changed” by heat & pressure From mountain building
Contact with magma

36. Metamorphic Rock

37. Metamorphic Rock

38. Metamorphic Rock Shale  slate  schist (if more H&P are added)
Shale or granite  gneiss
Limestone  marble

39. Shale to Slate Metamorphism
Metamorphic Rock
Shale to Slate Metamorphism

40. Metamorphic Rock

41. Marble

42. Poster Project:
Draw and color the Rock Cycle on a large Poster board.
Cut out pictures of the different kinds of rock shown and paste them to the drawing in the appropriate places.
Due in 1 week.