1. Identifying minerals
(with slides from ‘duncanpatti’ and ‘ms. Wells’)

2.  A mineral:
 1. Occurs naturally (not man-made)
 2. is a solid
 3. is a chemical compound arranged in an
orderly pattern (crystals)
 4. is inorganic (not made from dead plants or
animals)
 5. Is an element or a compound
What are minerals?

4. Properties of Minerals:
Which are the most important?
 Streak
 Luster
 Cleavage or Fracture
 Density
 Hardness

5. Physical Properties of Minerals
(can be used to identify the mineral)
Color
 Can be misleading
 Can vary with the type of impurities

6. Physical Properties of Minerals
(can be used to identify the mineral)
Luster
 Surface reflection
 metallic = shiny like
metal
 non-metallic = dull,
non-shiny surface
Pyrite has a metallic luster
Calcite has a non-metallic luster

7. Metallic Luster

8. Nonmetallic Luster

9. Physical Properties of Minerals
(can be used to identify the mineral)
Streak
 The color of the powdered
form of the mineral
 The color of the streak can be
different than the mineral
 Minerals must be softer than
the streak plate

10. Streak…can help identify quartz
http://www.childrensmuseum.org/geomysteries/cube/b3.html

11. Breaking Properties:
Cleavage or Fracture
• Cleavage – mineral
breaks along a flat
surface or into
sheets
• Fracture – when a
mineral breaks
with lots of jagged
edges

12.  Hardness = resistance to scratching
 Hardness does not concern brittleness
 (brittle = breaks apart easily)
 e.g. glass is brittle (breaks easily when
dropped), but it is harder than copper, i.e.
it can scratch copper.
 copper cannot scratch glass
Mineral test #1: hardness

13. Physical Properties of Minerals
(can be used to identify the mineral)
Hardness
 How easily a mineral scratches
materials
 Mohs Hardness Scale
• Scale from 1 (softest) to 10 (hardest)
• Test by seeing if the mineral can scratch
different objects (like human fingernail,
copper, penny, glass, steel file)

14. Talc(Mg3Si4O10(OH)2)

15. Gypsum (CaSO4·2H2O)

16. Calcite CaCO3

17. Fluorite CaF2

18. Apatite Ca5(PO4)3(F,Cl,OH)

19. Feldspar KAlSi3O8 - NaAlSi3O8 -
CaAl2Si2O8

20. Quartz SiO2

21. Topaz Al2SiO4(F,OH)2

22. Corundum Al2O3

23.  (do you really need a picture?)
Diamond

24.  cleavage: tendency of a mineral to split
easily or separate along flat surfaces
e.g. mica: 1 cleavage
feldspar: 2 cleavages
calcite: 3 cleavages
galena: 3 cleavages
Mineral test #2: cleavage

25. Physical Properties of Minerals
(can be used to identify the mineral)
Cleavage & Fracture
• The way the mineral breaks
• Cleavage—minerals break
along smooth, flat surfaces
and every fragment has the
same general shape
• Fracture—minerals that break
at random with rough or
jagged edges

28. Cleavage or Fracture?
1.
4.
3.
2.

29.  Specific gravity: “how dense is the mineral
compared to water?”
 Nearly all minerals are denser than water.
Mineral test #3: specific gravity

30.  If a mineral is denser than water, its
specific gravity is greater than 1.
 If it is less dense than water, its specific
gravity is less than 1.
 If it is equally dense as water, its specific
gravity equals 1.
specific gravity, cont’d

31. Extra Special Properties
1. Fluorescence
• Fluorescent color under ultraviolet (UV) light
2. Magnetic
• Attract magnets
3. Acid reaction
• Carbon dioxide gas bubbles off when you drop
acid on them
• Carbonates!

32. Fluorescence

33. Magnetic

34. Carbonate Acid Reaction