1. Chapter 2 – Section 2 Mineral Identification Please open your book to page 36. Please take notes over the yellow slides!

2. Identifying Minerals
How do you recognize someone you know? You may be able to identify them by their hair color, height, weight, facial features, etc.
Individual minerals also have characteristics that distinguish one from another.

3. Physical Properties Mineral Appearance & Color Hardness Luster
Specific Gravity
Streak
Cleavage and Fracture

4. Mineral Appearance & Color
Two obvious clues used to identify minerals
These clues are not enough to correctly identify a mineral

5. Mineral Appearance & Color
For example – Which one of the following is gold?

6. Mineral Appearance & Color
The one on the left is gold and the one on the right is pyrite (also known as fool’s gold).
Because they both look like gold, you cannot go just go by appearance and color to identify the mineral.
Other tests need to be performed
Gold
Pyrite (fool’s gold)

7. Hardness A measure of how easily a mineral can be scratched
Talc is so soft it can be scratched with your fingernail.
Diamonds are the hardest substance on Earth and can only be scratched by other diamonds.
So how do we tell how hard a mineral is?

8. Moh’s Hardness Scale (pg. 37)
A scale developed by Austrian scientist Friedrich Mohs that lists a list of common minerals and their hardness.

9. Let’s say you have a clear, whitish material that you know is either fluorite or quartz…but your not sure because they have the same appearance and color.
You try to scratch it with your fingernail but it doesn’t scratch. So you know that whatever it is, it has a hardness greater than 1.

10. You then try to scratch it with the iron nail and you are able to scratch the surface. So you can conclude that the hardness of the clear, whitish material has to be greater than 2.5 but lower than 4.5.
You can determine that the hardness of the unknown material is between 3 and 4. Well you already know that quartz has a hardness of 7 so the mystery material has to be fluorite.
Fluorite
Quartz

11. Let’s Take Some Notes!! Appearance & Color Hardness
These clues are NOT enough to correctly identify a mineral
 Hardness
A measure of how easily a mineral can be scratched

12. Luster The way a mineral reflects light.
Either metallic or nonmetallic

13. If it’s shiny like metal – it’s metallic
Hematite
Graphite
Pyrite
If it’s dull, glassy, pearly, or silky - it’s nonmetallic
Biotite
(Pearly)
Talc
(Silky)
Obsidian
(Glassy)

14. Let’s Take Some Notes!! Luster
The way a mineral reflects light (can be metallic or nonmetallic)

15. Specific Gravity
The specific gravity of a mineral is the ratio of its weight compared with the weight of an equal volume of water (very similar to density).
Gold has specific gravity of 19
It means gold is 19 times heavier than water.
19 times heavier

16. Specific gravity

17. Let’s Take Some Notes!! Specific Gravity
The ratio of the minerals weight compared to the weight of an equal volume of water (similar to density)

18. Streak
When a mineral is rubbed across a piece of porcelain tile (called a streak plate). A streak of powdered mineral is left behind.

19. The streak test only works for materials that are softer then the plate. The streak plate has a hardness of 7 so you can only test minerals that have a hardness below 7.
Gold and pyrite can be determined using a streak plate. Gold leaves a yellow streak and pyrite leaves a greenish black or brownish black streak.
Some minerals may appear as one color but leave a completely different color streak.
Some minerals will leave a streak on paper…like the graphite in your pencil

20. Let’s Take Some Notes!! Streak
The color of the mineral when in powdered form (streak plate)

21. Cleavage Cleavage is the way that mineral breaks.
Minerals that break along smooth, flat surfaces have cleavage.
The way the atoms are arranged make for a smooth, clean break.
Mica has cleavage

22. Fracture
Mineral that breaks uneven, rough, or jagged surfaces have fracture.
Quartz has fracture

23. If you were to take a layered cake and separate its layers, we would say that the cake has cleavage. But if we were to take our hand and jab it into the cake and pull it out, we would say that the cake has fracture.

24. FRACTURE
CLEAVAGE

25. Let’s Take Some Notes!! Cleavage & Fracture
Cleavage – minerals that break along smooth flat surfaces
Fracture – minerals that break unevenly & jagged

26. Other Properties
Some minerals are magnetic, such as magnetite, which is attracted to magnets.
In calcite – light forms two separate rays as it passes through causing you to see a double image.
Calcite will also fizz if you put some drops of hydrochloric acid on it.

27. Let’s Watch a Video!