1. Identifying Minerals
Section 5.2

2. Objectives
Describe seven physical properties that help distinguish one mineral from another.
List 5 special properties that may help identify certain minerals

3. Physical properties of minerals are a result of the chemical composition and crystalline structure

4. Talc is highly variable, yet Sulfur is almost always yellowish.
Color: Can be very characteristic for a few minerals, but is not important for others
Talc is highly variable, yet Sulfur is almost always yellowish.
Talc
Sulfur
Talc

5. Luster: the way light is reflected either Metallic or Non-metallic

6. Non-metallics are further described as:
dull (earthy)
waxy
glassy
(transparent)
pearly
(translucent)

7. Hematite has a very red streak
Streak: the color of the powdered mineral
Hematite has a very red streak

8. Cleavage and Fracture how a mineral splits or how a mineral breaks

9. The Six Crystal Systems
Isometric Orthorhombic
Tetragonal Hexagonal
Monoclinic Triclinic

10. Isometric System
Three axes of equal length intersect at 90 degree angles.
Examples: Galena, halite, and pyrite.

11. Pyrite and Halite

12. Tetragonal System Three axes intersect at 90 degree angles.
Horizontal axes of equal length.
Vertical axis can be longer or shorter than the other two.
Examples: Cassiterite, chalcopyrite, and zircon.

13. Cassiterite and Zircon

14. Orthorhombic System
Three axes of different lengths intersect at 90 degrees.
Examples: Olivine, topaz, and staurolite.

15. Olivine (Peridot) and Topaz

16. Hexagonal System
Three horizontal axes of the same length intersect at 60 degree angles
The vertical axis may be longer or shorter than the horizontal axes.
Examples: Calcite, hematite, and quartz.

17. Calcite and Quartz (Amathyst)

18. Monoclinic System
Three axes of different lengths, two intersect at 90 degree angles.
The third axis is oblique (inclined) to the others.
Examples: Micas, gypsum, microcline (orthoclase)

19. Gypsum and Orthoclase (Amazonstone)

20. Triclinic System
Three axes of unequal length that are oblique (inclined) to each other. No 90 degree angles.
Examples: Plagioclase feldspars, turquoise, and axinite.

21. Moh’s Hardness Scale

22. We use a scale from 1 to 10 called MOH’S SCALE OF HARDNESS.
Talc is a 1 and diamond is a 10.
Most minerals fall between The field scale can be very helpful:

23. Field Scale of Hardness
Finger Nail 2.5
Penny
Nail or Knife to 5.5
Glass to 6.0

24. Specific Gravity (heft):
Density = Mass/Volume
SG = Density of Sub./Density of H2O
Dry weight of Mineral
SG = Dry weight - weight in water

25. Example low and high Specific Gravity
Galena (high)
Graphite (low)

26. Unique Characteristics of a few minerals

27. Magnetism:
Some minerals are attracted to a magnet.
Magnetite

28. Fluorescence:
Minerals which will glow under an ultraviolet (black) light.
Opal
Minerals that continue to glow after the ultraviolet light is cut off are called phosphorescent.

29. Chatoyancy and Asterism
Chatoyancy: Silky appearance due to large numbers of parallel mineral fibers.
Asterism: Six-sided star shape when the mineral reflects light.

30. Radioactivity:
Some radioactive minerals will emit charged particles that are detected by a geiger counter.
Uranitite

31. Malleability: Some minerals are bendable Some minerals are brittle
Copper
Garnet

32. Feel:
Some minerals feel greasy or soapy (unctuous)
Graphite

33. Solubility:
Some minerals are soluble (will dissolve) in water
Halite

34. Iceland Spar (Calcite)
Double Refraction:
Optical properties reveal a double image
Iceland Spar (Calcite)

35. Taste:
Some minerals taste salty.
Halite

36. React with acids:
Carbonates react with hydrochloric acid and give off CO2 gas
Calcite