Download MINERALS

MINERALS
S6E5.b Investigate the
composition of rocks in
terms of minerals.
WHAT IS A MINERAL?
• A mineral is a naturally
formed, inorganic solid
that has a definite
crystalline structure.
Let’s Break it Down!!!
(FRAYER MODEL)
• Naturally formed = made in
nature/not “man-made”.
• Inorganic = non-living
• Solid = 3 dimensional, hard
• Definite crystalline structure =
made of two or more elements;
forms crystals.
CRYSTALS
• Solid, geometric forms of
minerals produced by a
repeating pattern of
atoms or molecules that is
present throughout the
mineral.
How Many Minerals Have
Geologists Discovered?
• Geologists have discovered over 2,500.
• However, we only see about 100
frequently.
• Less than 20 are widely distributed.
• 98.5% of the Earth consists of just eight
elements.
8 Elements of the Earth
1)
2)
3)
4)
5)
6)
7)
8)
Oxygen (46.6%)
Silicon (27.7%)
Aluminum (8.1%)
Iron (5%)
Calcium (3.6%)
Sodium (2.8%)
Potassium (2.6%)
Magnesium (2.1%)
Most Common Rock-Forming
Minerals
Quartz (SiO2)
Calcite (CaCO3)
Augite (Ca, Na)
Hematite (Fe2O3)
Micas
Feldspars
NATIVE ELEMENTS
• A mineral that is composed
of only one element.
• Ex: gold & silver
SILICATES vs. NONSILICATES
• Minerals divided into 2 groups
based on chemical composition
• Minerals that contain a
combination of silicon & oxygen
are silicate minerals.
• Silicate minerals make up more
than 90% of the Earth’s crust.
SILICATES vs. NONSILICATES
• Minerals that do not contain a
combination of silicon & oxygen
are nonsilicate minerals.
• Classes: native elements,
carbonates, halides, oxides,
sulfates, & sulfides.
IDENTIFYING MINERALS
• Color
• Luster
• Streak
• Cleavage & Fracture
• Hardness
• Density
• Special Properties
COLOR
•
•
•
•
What you see on the ouside!
Not the best way to identify a mineral
Same mineral can come in a variety of colors
Ex: Quartz---purest state is clear; impurities
can cause it to be different colors
• Exposure to air & water can change color (Ex:
pyrite---usually golden but changes to brown
or black when exposed to air & water)
LUSTER
• Luster: the way a surface reflects
light; whether a mineral is shiny or
dull!
• Metallic, submetallic or nonmetallic
luster
• Shiny = metallic luster
• Reflective/dull = submetallic
• Dull= nonmetallic luster
STREAK
• Streak: color of a mineral in powdered
form
• Rub mineral against a piece of unglazed
porcelain (streak plate)
• Mark left on streak plate is the streak.
• Color of streak not always the color of
the mineral sample.
• Not affected by air or water
• More reliable than color in identifying a
mineral
CLEAVAGE & FRACTURE
• How a mineral breaks
• Determined by arrangement of
atoms
• Cleavage: tendency to break along
smooth, flat surfaces (Ex: halite &
mica)
• Fracture: tendency to break
unevenly along curved or irregular
surfaces (Ex: quartz)
HARDNESS
• Mineral’s resistance to being scratched
• Mohs Hardness Scale
• Ranges from 1 to 10; 1 being softest
(talc) & 10 being the hardest (diamond)
• Scratch tests; scientists use common
items to test hardness.
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–
–
–
Fingernail has a hardness of 2-2.5
Knife blade is 3-4
Glass is 5-6
Steel file or nail is 6.5-7
A mineral of a given hardness will
scratch any mineral that is softer
than it is.
DENSITY
• The measure of how much matter is
in a given amount of space.
• Density is a ratio of an object’s
mass to its volume
• D=m/v
• Measured in grams per cubic
centimeter (g/cm3)
DENSITY
• Water has a density of 1g/cm3
• Used as a reference point for
other substances.
• Object sinks---it’s density is
greater than 1g/cm3
• Object floats---it’s density is
less than 1g/cm3
SPECIAL PROPERTIES
• Some properties are
particular to only a few types
of minerals
• Fluorescence, chemical
reaction, optical properties,
magnetism, taste,
radioactivity