1. Chapter 4.1 – Minerals and Their Properties
Minerals are the building blocks of rocks (which are usually mixtures).
Minerals are pure substances - elements or compounds, with specific chemical formulas that do not vary or only vary within a limited range.
About 3000 minerals are known.
Only about 10 are common in Earth's crust.
Most minerals form in the geosphere, but some minerals form in the hydrosphere or even the biosphere.

2. What is a Mineral?
The 3 criteria: 1) Naturally occurring substance, not manmade. 2) Inorganic – not made of anything that is/was living. 3) Solid and Crystalline in form.

3. What does “crystalline” mean?
The particles in minerals (atoms, ions, or molecules) are arranged at specific “lattice” positions.
The shape of a mineral crystal can reflect the internal structure but often does not.

4. What does “crystalline” mean?
Remember…a mineral can also be crystalline at the atomic scale without exhibiting crystal-like shapes.
It is still a “crystal”.

5. Mineral Properties help you to identify minerals!
Characteristic property - A physical or chemical property that is helpful in identifying a material (in this case, minerals). Ex. – Diamond’s extreme hardness and luster Ex. – Graphite’s greasy feel, softness, and metallic luster.

6. Mineral Properties help you to identify minerals!
Physical property – A quality that can an be measured without a chemical reaction occurring. Ex. Color, crystal shape, luster, hardness, density (specific gravity) Chemical property – reflect how something chemically reacts with something else; when tested, a chemical reaction will occur if it has that chemical property. Ex. Reactivity with acid, mineral composition

7. Minerals Properties are caused by…
The properties (characteristics) of minerals are determined by the structure (arrangement) and chemical composition of the particles inside the mineral.
Diamond
(C)
Graphite
(C)

8. Minerals Composition
Mineral composition refers to the ratios of elements present in the crystal – the chemical formula or chemical symbol.
Pyrite: FeS2
Quartz: SiO2
Calcite: CaCO3
Copper: Cu
Sulfur: S

9. Minerals: Characteristic Properties
Color- One of the most obvious mineral properties, but NOT the most useful.  Many minerals come in a large variety of colors.
Streak- The color left behind when mineral is scraped on unglazed porcelain (may be the same or a different color than the crystal).
Luster- The manner in which light reflects off surface of a mineral - metallic vs. nonmetallic (glassy, pearly, dull, earthy, silky).

10. Minerals: Characteristic Properties
Cleavage - the smooth breakage of a mineral along relatively weak planes of the crystalline structure.
Fracture – The rouch and irregular breakage of a mineral (choncoidal fracture).

11. Basal or platy cleavage
Prismatic
cleavage
Cubic
cleavage
Rhombohedral cleavage
Octahedral cleavage

12. Describe the Cleavage B A
Irregular Surface D C

13. Minerals: Characteristic Properties
Hardness- The scratch-resistance of a mineral based on a scale from 1 to 10.

14. Moh’s Scale of Hardness

15. Hardness Test Warning!
Don’t confuse a scratch with a streak. You can’t rub a scratch off!

16. Minerals: Characteristic Properties
Crystal Form (or Crystal Habit)
The geometric shape of a well-formed crystal (the growth shape if there was room to grow).

17. More Characteristic Properties of Minerals
Reactivity to acid- The chemical response of a mineral to hydrochloric acid, causing the mineral to fizz (effervescence).
Double Refraction – The ability to split light rays to produce two images.
Magnetism- The attraction to a magnet.
Density/Specific gravity- How heavy a mineral seems (for its size): High, medium, or low as determined by hefting.
Fluorescence – the ability to glow in the dark after exposure to ultraviolet light.
Irridescence – the ability to produce a play of colors.

18. Wash the specimen and dry it.
HCl Test
CaCO3 + 2HCl  CaCl2 + CO2 + H2O
Wash the specimen and dry it.
Wash your hands too!

19. Identifying Feldspars Alkali Series- Wavelets

20. Identifying Feldspars Plagioclase Series- Striations

21. Non-Silicate Minerals
Some noteworthy non-silicate minerals are:
Native elements- Composed entirely of one element (copper, gold, diamond).
Carbonates- Contain CO32- (calcite, CaCO3).
Sulfates- Contain SO42- in their structures (gypsum, CaSO4· 2H2O)
Sulfides- Contain S2- (but no O) in their structures (galena, PbS; pyrite FeS2)
Oxides- Contain O2- bonded to metal atoms (hematite, Fe2O3; magnetite, Fe3O4)

22. Chapter 4.2 - The Silicate Minerals
Five minerals (out of 3000) account for 90% of the minerals in Earth's crust.
These are:
Quartz
Feldspar
Pyroxene
Amphibole
Mica
All contain Silicon and Oxygen!

23. The Silicate Minerals
The silicate minerals all contain Si and O covalently bonded together to form a silicon-oxygen tetrahedron:

24. Silicate Mineral Structures
The basic structure for silicate minerals is a silicon-oxygen tetrahedron.
Contains 1 silicon at the center, and 4 oxygen atoms at the corners.
Each tetrahedron is negatively charged (SiO44-).

25. The extra negative charge (-4) means that positive metal ions like Mg, Ca, Fe, Al etc. are needed for charge balance (i.e., MgSiO3).
The metal ions go in between the silicate tetrahedra.

26. Different arrangements of the silicate tetrahedra 
5 major, different silicate structures.

27. Isolated Tetrahedra- No oxygen atoms are shared between tetrahedra.
Examples: Olivine, Garnet, Topaz

28. Single Chain silicates- 2 oxygen atoms on each tetrahedron are shared.
Example: Pyroxene

29. Pyroxenes Enstatite: MgSiO3 Ferrosilite: FeSiO3

30. Example: Amphibole (hornblende)
Double-chain silicate- Alternating 2 and 3 oxygen atoms on each tetrahedron are shared.
Example: Amphibole (hornblende)

31. Amphiboles Hornblende: Ca2(Mg,Fe,Al)5(Al,Si)8O22(OH)2

32. Sheet silicates- 3 oxygen atoms on each tetrahedron are shared.
Examples: Biotite, Muscovite, Talc, Clays

33. Micas Biotite: K(Fe,Mg)3AlSi3O10(F, OH)2

34. Micas Muscovite: KAl2(AlSi3O10)(F,OH)2

35. Talc (Mg,Fe)3Si4O10(OH)2

36. Examples: Quartz, Feldspar
Framework silicates- All 4 oxygen atoms on each tetrahedron are shared.
Examples: Quartz, Feldspar

37. Quartz (SiO2)
(Fixed composition)

38. (Somewhat variable composition)
Feldspar Group Minerals K-Feldspar: KAlSi3O8 Albite: NaAlSi3O8 Anorthite: CaAl2Si2O8
(Somewhat variable composition)

39. Gemstones
What properties of minerals make certain specimens suitable for jewelry (gemstones)?

40. Gemstones Attractive color/transparency. High hardness. Good cleavage.
Rarity.

41. Gemstones Have “Special” Names
Mineral name: Quartz
Gemstone name: Amethyst

42. Gemstones Have “Special” Names
Mineral name: Olivine
Gemstone name: Peridot

43. Gemstones Have “Special” Names
Mineral name: Corundum
Gemstone name: Ruby or Sapphire