1. An Introduction to Minerals

2. Atoms
Atoms – basic building blocks for all earth materials; consist of 3 basic components: protons, neutrons, electrons

3. Atoms combine to form Elements
Elements – fundamental component that can not be broken down into other substances by ordinary chemical processes
Elements combine to form minerals

4. General Facts About Minerals
2,000 + minerals have been identified
A few are “native elements” -- made of only one element, such as sulfur, gold. copper, and graphite (carbon)
Most are compounds, especially the silicate group (Si, O).
Other important groups are oxides, carbonates, and sulfides.

5. MINERALS NATIVE ELEMENTS Gold (Au) Silver (Ag) Gold Platinum (Pt)
Diamond (C)
Graphite (C)
Sulfur (S)
Copper (Cu)
Gold
Copper
Silver

6. Mineral Criteria 1. Crystalline solid 2. Naturally occurring
3. Have a definite chemical composition
4. Inorganic

9. Minerals are identified by their Physical Properties
Crystal Form
Color
Streak
Luster – metallic, non-metallic
Hardness – Moh’s Hardness Scale (1-10)
Cleavage
Fracture
Specific Gravity
Others

10. A mineral’s physical properties are controlled by its internal arrangement of atoms
regularly repeating, orderly pattern

11. The most common crystalline structure
Silica-oxygen tetrahedron – basic building block for silicate minerals

12. Silica tetrahedron combine several different ways
Five major types of silicate minerals based on their structure
Isolated tetrahedron
Single chain
C) Double chains
D) Sheet silicates
E) 3-D framework silicates

15. Minerals can have the same chemical composition (Carbon) but different physical properties because of their crystal structure
Diamond Graphite

16. COLOR Color is not usually a definitive property of a mineral.
Some minerals have characteristics colors
Others vary due to chemical differences or impurities (atoms mixed inside the main elements)
However most minerals have a variety of colors.
The mineral sphalerite can be yellow, black, red, green or varieties thereof.
Quartz is usually colorless, however it can have many colors depending on trace amounts of cations that substitute in the structure.

17. Some Colors of Quartz

18. STREAK
For opaque minerals, if you rub the sample across a streak plate, it will leave a colored powder. This streak is distinctive for minerals and is used to identify minerals.
Hematite can be brown, black, metallic gray and earthy but in all cases it gives a red-brown streak.

19. Varieties of Hematite – all same color streak

20. HARDNESS – Mineral’s resistance to scratching
HARDNESS – Mineral’s resistance to scratching. Minerals with higher numbers will scratch minerals below
The last three are not common minerals. Fingernail is 2 to 2.5, Cu penny is around 3.5; hammer is about 5.1, knife is 5.2 and plate glass is 5.5.

21. LUSTER Metallic does not mean shiny
Describes how light reflects off the surface
Categories: Metallic or non-metallic
Metallic does not mean shiny
Non-metallic: vitreous or glassy; silky; resinous; pearly; greasy; waxy, dull; earthy

22. Examples of metallic luster

23. More Examples of Metallic Luster
Pyrite (FeS2)
Galena (PbS)
PYRITE
GALENA

24. Example of non-metallic luster
Vitreous--quartz

25. Example of non-metallic luster
Silky--example plagioclase feldspar

26. Non-metallic and metallic luster – earthy hematite – metallic hematite

27. Cleavage and Fracture
Some minerals split along flat surfaces when struck hard--this is called mineral cleavage
Other minerals break unevenly along rough or curved surfaces--this is called fracture
A few minerals have both cleavage and fracture ( mica )

28. Cleavage
Halite (NaCl)
Fluorite (CaF2)
HALITE
FLUORITE

30. Cleavage
MUSCOVITE
BIOTITE

31. Rose Quartz – Conchoidal Fracture

32. Conchoidal Fracture - Quartz
Obsidian

33. DENSITY / SPECIFIC GRAVITY
This is the ratio of the density of the mineral to the density of water.
Weight Air/(Weight Air-Weight in water) = specific gravity
It is obtained by weighing a piece of mineral in air and then in water. The difference in weight is equal to the volume of water displaced.

34. Acid Test for Carbonates
Special Characteristics:
Carbonates react with dilute HCl and other acids by fizzing or bubbling (releasing CO2 gas)

35. MINERALS NONSILICATE MINERALS CARBONATES
Carbonate ion (CO32-) is prominent in minerals.
Has -2 charge.
Combines readily with positive ions.
Bonds generally weak.
Minerals are soft (3-4).
Minerals are soluble in acidic water.
Leads to cave development.
Calcite (CaCO3)
Dolomite (CaMg(CO3)2)
CALCITE
DOLOMITE

36. Less than a dozen are common in most rocks
Quartz
Feldspar (group)
Muscovite (silver white mica)
Biotite (black mica)
Calcite
Pyroxene
Olivine
Amphibole (group)
Magnetite, limonite, and other iron oxides
Pyrite

37. Common uses include: Aluminum--packaging, transport, building
Beryllium--gemstones, fluorescent lights
Copper--electric cables, wires, switches
Feldspar--glass and ceramics
Iron--buildings, automobiles, magnets
Calcite--toothpaste, construction