5.3IDENTIFYING MINERALS
Objectives:
1) What do scientists look for when identifying minerals
2) Describe 3 simple tests scientists use to identify
minerals.
KEY IDEA Minerals can be identified by physical
and chemical propertiesColorLusterCrystal shapeStreakCleavageFractureHardnessSpecific gravityReaction to an acid
INTRODUCTION Mineralogy: the
study of minerals and their properties
Many minerals can be identified and classified by Inspecting
visuallyDoing simple
tests to find properties
ROCK-FORMING MINERALS
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
IDENTIFYING MINERALS BY INSPECTION A field guide is
usefulLists properties
Color Luster Crystal shape
Rarely is a mineral identified by a single property
IDENTIFYING MINERALS BY INSPECTION CONT’D
ColorThe 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
IDENTIFYING MINERALS BY INSPECTION CONT’D Luster: the way the
mineral shines in light Metallic
Shines like polished metal
Nonmetallic Several categories
Vitreous Pearly Adamantine Greasy Oily Dull Earthy
TESTING MINERAL SPECIMENS Simple physical
testsStreakCleavageHardnessSpecific gravity
TESTING MINERAL SPECIMENS CONT’D
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
TESTING MINERAL SPECIMENS CONT’D
Cleavage: tendency to split easily along flat surfacesUseful b/c surfaces can be observed even on
tiny mineral grains
TESTING MINERAL SPECIMENS CONT’D
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)
TESTING MINERAL SPECIMENS CONT’D
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
TESTING MINERAL SPECIMENS CONT’D 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
TESTING MINERAL SPECIMENS CONT’D
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
SPECIAL PROPERTIES OF MINERALS Double refraction:
splits light rays that pass through it so 1 object will look like 2 when looking through the specimen
SPECIAL PROPERTIES OF MINERALS CONT’D
Fluorescent: appearing to glow when viewed under ultraviolet light
Phosphorescent: continue to glow after the ultraviolet light is turned off
5.3 EXIT TICKET 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.
Top Related