Geology
Rocks, Minerals,
Volcanoes, & Earthquakes
Minerals
Naturally occurring
Inorganic solid ( not from living
matter)
Has a definite structure; crystals
Has a definite composition; a
compound or element.
Minerals
Crystals =is a solid in which atoms are
arranged in repeating patterns.
NaCl, table salt , forms a cubic crystal.
Wulfenite forms a tetragonal crystal.
Corundum = Hexagonal
Gypsum = Monoclinic
Topaz = Orthorhombic
Topaz
Mineral : How they form…
1. Hot magma ( melted rock) cools to
form minerals.
The types and amounts of elements
in the magma determines which
minerals form.
2. Crystals form from minerals dissolved
in liquids.
When the liquid evaporates, mineral
crystals are left behind.
How Minerals Form:
3. Precipitation out of solution is the
third way.
Mineral Composition
There are 90 elements that occur naturally;
98% of the Earth’s crust is made of only eight
of these elements.
Oxygen is 46.6%
Silicon is 27.7%
Aluminum is 8.1%
Iron is 5%
Calcium is 3.6%
Sodium is 2.8%
Potassium is 2.6%
Magnesium is 2.1%
Mineral Groups
There are about 4000 minerals.
Most of the common minerals are in the
group called silicates.
Silicates contain silicon, oxygen and
one or more other elements.
Quartz and Feldspar are common
rock-forming minerals in the silicate
group.
Feldspar
Quartz
Mineral Groups
Carbonates
Oxides
Sulfides
Sulfates
Halides
Hydroxides
Phosphates
Mineral Identification
Appearance
Hardness
Luster
Color
Streak
Fracture
Cleavage
Other Properties
Mineral Properties
Appearance – Color and general
appearance can help to identify a
mineral.
Many minerals look very similar.
Many minerals are found in different
colors.
Other properties must be used to
identify minerals.
Mineral Properties
Hardness = The Mohs Scale of
Hardness measures how easily a
mineral can be scratched.
Talc is the softest, a 1 on the scale.
Diamonds are the hardest, a 10.
Talc
Mineral Properties: Hardness
Mohs Scale
Mineral Properties:Luster
Luster: how light is reflected from a
mineral’s surface.
Metallic Luster = shines like metal
Nonmetallic Luster = any mineral that
does not shine like metal.
Nonmetallic can be : dull, pearly, or
silky.
Orthoclase
Galena
Luster
Mineral Properties: Streak
Streak is the color of the mineral when it
is broken up and powdered.
The mineral is rubbed across a white,
unglazed, porcelain tile.
Minerals harder than the streak plate (7)
will not have streak.
Graphite (pure carbon) has streak on
paper. It is used in pencils, not lead.
Mineral Properties: Cleavage
and Fracture
Minerals that break with rough or jagged
edges have fracture.
Minerals that break along smooth , flat
surfaces have Cleavage.
Some minerals have unique
properties;
Magnetite is magnetic, Calcite fizzes
with HCl ( acid).
Mineral Properties: fracture
21.Limestone = even
22. Serpentine = uneven
23. Obsidian = conchoidal
24. Rose Quartz = sub-conchoidal
25. Tremolite = splintery
26. Copper = hackly
Types of Cleavage
Mineral Properties: Cleavage
15. Mica = Basal ( one direction)
16. Feldspar = Pinacoidal ( two
directions)
17. Amphibole = Prismatic ( Two
directions at 124o and 56o
Cleavage
18. Halite = Cubic ( Three directions, at
right angles)
19. Calcite = Rhombohedral ( Three
directions not at right angles.)
20. Fluorite = Octahedral ( four
directions)
Uses of Minerals Jewelry on the Web
Gems are rare and beautiful minerals
which are cut and polished for jewelry.
Differences between gems and
common minerals are small: Amethyst
is a gem form of quartz (SiO2) with
manganese traces. The Mn gives
amethyst its purple color.
Uses of Minerals
Ores is a mineral that is useful, and can
be mined for profit.
Bauxite is a mineral ore used to make
aluminum.
Hematite is a mineral ore source for
iron.
Uses For minerals
Minerals in Your House(Web)
Copper is used for coins, wires, pipes
and cooking tools.
Ilmenite and rutile are mineral ores
which provide titanium. It is used for hip
replacements, bicycles, and airplane
parts
Science and Art
Minerals are in paint pigments, crayons,
pastels, chalks, clays, and glazes.
Cinnabar is used for red.
Malachite and Azurite are used for
greens and blues.
By Salvador Dali
Science and Art
Lapis Lazuli is used for dark blues.
Ochre is used for yellows and reds
By Salvador Dali