1. Aim: How can we describe a mineral?

2. Turn and Talk
Take one minute with your partner next to you and discuss what you think a mineral is.

3. Minerals

4. So what is a mineral? A mineral must meet the following five characteristics. All rocks are made of minerals What are the 5 characteristics of all minerals?

5. Mineral
Characteristics

6. 1. A mineral occurs naturally.

7. 2. A mineral is solid.

8. 3. A mineral has a definite chemical composition.

9. 3. A mineral has a definite chemical composition.
Find the ESRT page that deals with minerals.
What is the composition of halite?
Quartz

10. TTYP
What are the two most common elements in all minerals?

11. Average Crustal Composition
What two elements are the most abundant by mass in the crust?
Oxygen
Silicon

12. 4. A mineral’s atoms are arranged in an orderly pattern.

13. 5. A mineral is inorganic (was never alive)

14. Mineral or Not?
Gold
Water
Pearls

15. Mineral or Not?
Coal
Diamond
Silver

16. These minerals make up most of the rocks found in the Earth’s crust.

17. Of the almost 4000 known minerals, only about 30 are common
Of the almost 4000 known minerals, only about 30 are common. The most common are
quartz
feldspar
mica
calcite

18. Minerals are arranged into groups…
According to their chemical and physical properties.

20. Mineral Groups Silicates Other groups include:
The most common (silicon & oxygen)
Other groups include:
Carbonates
Sulfides
Oxides
Halides
Hydroxides
Sulfates
The molecular structure is called a silica tetrahedron

21. The importance of Minerals
Without a proper intake of zinc the immune system can become vulnerable and normal human growth can be delayed. Zinc also plays a key role in our ability to heal wounds

22. Turn and Talk
With your partner look at p. 16 of your reference table and find some common uses for minerals.

23. Identification of Minerals

24. To be able to identify these and other minerals, we need to look at the properties used to separate and distinguish these minerals.

25. Identifying Minerals
Remember!: You cannot identify a mineral only using one property. These properties need to be considered together to correctly identify a mineral.

26. 1. Color
What color the mineral is.
Color is the most easily observed mineral property and the least useful!

27. Many minerals have a similar color.

28. Colors
Many minerals can turn colors due to impurities, or they can change colors in various circumstances.

29. Color
For example, pure quartz is colorless or white, impurities can make the mineral rose, purple or pink!

30. Some exceptions to the color rule would be cinnabar, which is always red, and malachite, which is green.

31. 2. Streak
Streak of a mineral is the color of its powder when rubbed on an unglazed white tile. Test: rub the mineral on a tile.

32. Streak
The streak is often not the same color as the mineral. A minerals color may vary, but the streak rarely will!

33. 3. Luster
Luster refers to the way a mineral shines in reflected light. Notice the difference between these two minerals?

34. 3. Luster
The mineral on the left has a metallic luster, the one on the right, a nonmetallic luster.

35. Metallic or Non-metallic?
Galena

36. Metallic or Non-metallic?
Quartz

37. Metallic or Non-metallic?
Pyrite aka fool’s gold

38. 4. Hardness
The hardness of a mineral is its resistance to being scratched. Diamond is the hardest of all minerals, and talc is the softest.
The harder one will always scratch the softer one

39. Common hardness tests Unpolished finger nail = 2.5 Steel = 4.5
Glass = 5.5

40. 4. Hardness
Friedrich Mohs devised a hardness scale. In this scale, ten well known minerals are given numbers from one to ten. Lets take a look at the ten minerals used and some of the simple tests.

41. Hardness
Talc (left) is the softest and has a hardness of 1. A soft pencil lead will scratch talc.
Gypsum is a bit harder and has a hardness of 2. A fingernail scratches gypsum.

42. Hardness
Calcite (left) has a hardness of 3 and a copper penny just scratches it.
Fluorite has a hardness of 4 and it can be scratched by an iron or brass nail.

43. Feldspar has a hardness of 6 and it will scratch a window glass.
Apatite (left) has a hardness of 5 and can be scratched by a steel knife blade.
Feldspar has a hardness of 6 and it will scratch a window glass.

44. Topaz has a hardness of 8 and will scratch quartz.
Quartz (left), with a hardness of 7, is the hardest of the common minerals. It easily scratches hard glass and steel.
Topaz has a hardness of 8 and will scratch quartz.

45. Corundum (left) has a hardness of 9. Corundum will scratch topaz.
Diamond with its hardness of 10 can easily scratch the rest of the minerals.

47. Hardness finder! Find a mineral that is softer than calcite.
Find a mineral that would scratch quartz.
Find a mineral that fluorite would scratch.

48. On your own
Create two questions using the hardness scale.

49. 5. Cleavage
The cleavage of a mineral is its tendency to split easily or to separate along flat surfaces. Cleavage can even be observed on tiny mineral grains making it a very useful property!

50. 5. Cleavage
Mica is probably the best example as it splits into thin sheets. It is said to have one perfect cleavage.

51. Cleavage
Feldspar splits readily in two directions, always at or near right angles.

52. Not all minerals show cleavage.
Those that don’t break along cleavage surfaces are said to have fracture.

53. Cleavage or Fracture?
Cleavage
Halite

54. Cleavage or Fracture?
Fracture
Quartz

55. Cleavage or Fracture?
Cleavage
Biotite Mica

56. Cleavage or Fracture?
Fracture
Olivine

57. 6. Reaction to Acid
Calcite is calcium carbonate, CaCO3. If a drop of weak hydrochloric acid is placed on calcite, the acid bubbles as carbon dioxide is released.

58. 7. Other special properties
Magnetic
Malleable
Radioactive
Flourescence
Taste

59. Turn and talk: Looking at the samples below and what you’ve learned about minerals today what properties do you think you would use to identify them?