1. Objectives: 1) What do scientists look for when identifying minerals 2) Describe 3 simple tests scientists use to identify minerals.

2.  Minerals can be identified by physical and chemical properties  Color  Luster  Crystal shape  Streak  Cleavage  Fracture  Hardness  Specific gravity  Reaction to an acid

3.  Mineralogy: the study of minerals and their properties  Many minerals can be identified and classified by  Inspecting visually  Doing simple tests to find properties

4.  Almost 4000 known minerals  About 30 are common  Rock-forming minerals: a specific group of minerals known to form rocks  Rocks are often made of many minerals  Identify a mineral by looking at the physical properties  Tests can identify chemical properties of minerals

5.  A field guide is useful  Lists properties Color Luster Crystal shape  Rarely is a mineral identified by a single property

6.  Color  The least useful property for mineral identification Many minerals have similar colors Impurities can turn colorless minerals into colored minerals Some minerals change color in various circumstances

7.  Luster: the way the mineral shines in light  Metallic Shines like polished metal  Nonmetallic Several categories Vitreous Pearly Adamantine Greasy Oily Dull Earthy

8.  Simple physical tests  Streak  Cleavage  Hardness  Specific gravity

9.  Streak: a mineral is the color of its powder  Rub the mineral on an unglazed white tile (streak plate)  The color of a mineral may vary but the streak rarely does  Metallic mineral streak is at least as dark as the specimen  Nonmetallic streaks are colorless or white

10.  Cleavage: tendency to split easily along flat surfaces  Useful b/c surfaces can be observed even on tiny mineral grains

11. Irregular Fracture  Fracture: when minerals break in directions other than along cleavage surfaces  Conchoidal (smooth and curved)  Splintery (jagged surface w/sharp edges  Uneven or irregular (generally rough surface)

12. Talc  Hardness: resistance to being scratched  Friedrich Mohs made a number scale to determine hardness of a mineral  Range of 1-10  Softest-hardest  Talc-Diamond  1 limitation The increase in hardness at each step is not uniform

13.  Specific gravity: the ratio of its mass to the mass of an equal volume of water  Tells how many times denser the mineral is than water Density: the ratio between a substance’s mass and its volume  Nonmetallic minerals have specific gravities less than those of ore minerals and native metals

14.  Buoyancy: the tendency of an object to float in water  Archimedes’ Principal: an object will weigh less when it is in water then when it is in air and that this difference is equal to the weight of the displaced water A mineral sample will displace an amount of water equal to its own volume

15.  Double refraction: splits light rays that pass through it so 1 object will look like 2 when looking through the specimen

16.  Fluorescent: appearing to glow when viewed under ultraviolet light  Phosphorescent: continue to glow after the ultraviolet light is turned off

17.  Answer the following questions.  Use complete sentences.  You may NOT use your book. You MAY use your notes.  This is a quiz grade. 1) What do scientists look for when identifying minerals 2) Describe 3 simple tests scientists use to identify minerals.