Chapter 5 - Minerals
• What is a mineral?
• Occurs naturally
• Is a solid
• Has a definite
composition
• Its atoms are
arranged in an
orderly fashion
• Is inorganic (never
been alive)
• Most minerals….
• …are compounds
• That means that
they are made up of
more than one
element
• 2 most abundant
minerals in Earth’s
crust are….
• Oxygen & silicon
• 8 elements make up
most of the minerals
in Earth’s crust
• (oxygen, silicon,
aluminum, iron,
calcium, sodium,
potassium &
magnesium)
• How do minerals
form?
• Some form from
magma - molten
rock
• Others form in or
near water
• Structure of
minerals…..crystals
• Crystals are a
regular geometric
solid with smooth
faces
• There are 6 crystal
shapes….some are
“tougher” than the
others
• Crystal Shapes
•
•
•
•
•
•
Cubic
Orthorhombic
Tetragonal
Triclinic
Hexagonal
Monoclinic
• For example,
diamonds and
graphite are both
pure carbon,
but…….
• Diamonds are
Tetrahedral - very
hard
• Graphite is
hexagonal - very
soft
• Silicates
• Rock-forming
minerals
• Compounds made
up of silicon and
oxygen
• Most rock-forming
minerals are
silicates (the
minerals that make
up most rocks)
• Silica Tetrahedron
• 4 oxygen atoms
packed around 1
silicon atom
Identifying Minerals by
physical properties
• Cleavage
• The ability to split
along planes, in
particular directions
• To “peel”
• Luster
• The ability to shine
under light
• Streak
• The color of a
mineral’s powder
• Fracture
• To break along noncleavage surfaces
• To “splinter”
• Specific Gravity
• The ratio of a
mineral’s weight to
an equal volume of
water
• Use a spring scale
to measure
• Hardness
• Moh’s hardness
scale
• The resistance to
scratching
• Ranges from 1 to 10
• 1 is the softest - Talc
• 10 is the hardest Diamond
• Special properties
• Birefringence double refraction
• Phosphorescence the ability to glow
under UV light