Download Chapter 9

CHAPTER 9: MINERALS OF THE EARTH’S CRUST
What is a mineral?
A mineral:
• is inorganic
• is naturally occurring
• is a crystalline solid
• has a definite chemical
composition
to 9.1
Inorganic?
• Inorganic means that it is not made by a
living organism.
• Coal is made from the remains of plants.
• Coal is NOT a mineral because it is NOT
inorganic.
to “What is a Mineral?”
Naturally Occurring?
• Steel and brass are compounds made by
humans.
• Steel and brass are not found in nature
• Steel and brass are NOT naturally
occurring and so they are NOT minerals.
to “What is a Mineral?”
A Crystalline Solid?
• A solid is the physical form of matter with a
definite shape and volume.
• Crystalline means the atoms are arranged in a
regular and repeating pattern:
Definite Chemical Composition?
• Calcite consists of calcium, carbon, and
oxygen in definite amounts. Calcite is a
mineral
• Concrete consists of cement, gravel, sand,
and water. The amounts of each can vary
depending on what you are using the
concrete for. Concrete is not a mineral
to “What is a Mineral?”
The Two Main Mineral Groups
1. Silicates:
Minerals that contain silica (silicon [Si] and
oxygen [O] combined), and usually some
other element(s). Silicate minerals make
up 96% of the earth’s crust. Most
common are Feldspars.
2. Nonsilicates:
Minerals that do not contain silica.
to 9.1X
Most Common Elements
magnesium (Mg)
aluminum (Al)
silicon (Si)
oxygen (O)
sodium (Na)
potassium (K)
calcium (Ca)
iron (Fe)
to 9.1X
Six Nonsilicate Groups
1. Carbonates
•
•
Contain CO3 (carbonate group)
Examples calcite, dolomite
2. Halides
•
•
Contain a halide element (Group VIIA on the Periodic Table)
Examples halite, fluorite
3. Native Elements
•
•
Elements uncombined with other elements
Examples sulfur
4. Oxides
•
•
Contain oxygen and an element other than silicon
Examples hematite
5. Sulfates
•
•
Contain SO4 (sulfate group)
Example gypsum
6. Sulfides
•
•
Contain sulfur and another element
Examples galena, pyrite
to 9.1
Characteristics of Minerals
Color
Luster
Streak
Cleavage/Fracture
Hardness
Crystal Shape
Density
to 9.2
Color?
Easiest property to see, but seldom useful
Many minerals are the same color
quartz
feldspar
calcite
talc
Some minerals come in several colors
calcite
quartz
Color?
For a few minerals, color is a very good property for
identification! Here are some examples:
• pyrite
• sulfur
• galena
to “Characteristics”
Luster?
• Definition: light reflected
from the surface of a
mineral
• Two main types:
1. metallic—looks like polished
metal
2. nonmetallic—does not look
like polished metal!
to “Characteristics”
Streak?
• Definition: color of a mineral in
powdered form
• Rub the mineral on a piece of
unglazed ceramic tile (called a
streak plate)
• Most metallic minerals have
dark streak
• Most nonmetallic minerals have
white or light-colored streak
to “Characteristics”
Cleavage?
• Definition: splitting
of a mineral along
smooth, flat
surfaces
• Cleavage surfaces
form where atomic
bonds are weak
to “Characteristics”
Fracture?
• Definition: breakage along irregular surfaces
(absence of cleavage)
quartz
to “Characteristics”
Hardness?
• Definition: ability of a mineral to resist
scratching
Softest
What is the hardness
of a mineral that can
scratch feldspar but
not quartz?
6.5
Hardest
to “Characteristics”
Crystal Shape?
• Definition: the form taken by a mineral as a result of its
internal arrangement of atoms
• Flat surfaces on crystals are called “crystal faces.”
• Most crystals don’t show crystal faces because they
don’t have enough room to form.
amphibole
crystals
crystal faces on all sides
no crystal faces
to “Characteristics”
Density?
• Definition: the amount of matter in a given
volume of a substance (formula is: density =
mass/volume, or D = m/v)
• When you have two objects the same size, the
one that “feels heavier” has higher density, the
one that “feels lighter” has lower density.
• Go to Gizmo
to “Characteristics”
Special Properties of Minerals
• Magnetism
• Fluorescence and phosphorescence
• Double refraction
• Radioactivity
• Reaction to hydrochloric acid
to 9.2
Magnetism?
• Most common magnetic mineral is:
magnetite
• Sometimes magnetic:
pyrite (fool’s gold)
to Special Props
Fluorescence/Phosphorescence?
• Fluorescence
glows under ultraviolet light
• Phosphorescence
glows after ultraviolet light is turned off
to Special Props
Double Refraction?
• Transparent minerals that can split a light
ray into two parts (ex: calcite)
to Special Props
Radioactivity
• The breakdown of a nucleus because it is
unstable
• Caused by arrangement and number of
protons and neutrons in the nucleus
uraninite
processed uranium ore
uranium oxide
to Special Props
Mineral Resources
• Steel is made from iron and iron rich minerals (cars,
building material)
• Quartz (sand) used for making glass
• Alloys of magnesium and aluminum
• Titanium and molybdenum (aircraft and bicycles)
• Gemstones (diamonds for jewelry and cutting and
grinding tools)
• Graphite (pencils, paint,lubricants and batteries)
• Galena (lead) used in car batteries; in solder
Mineral Identification
• Mineral Identification Activity