Transcript Mineral Formation

Let’s Review…
5 Characteristics
• 1. Naturally occurring (why won’t a
cake work…?)
• 2. Inorganic (can it come from once
living things?)
• 3. Solid (how about a liquid or a gas?)
• 4. Crystal Structure (look at it under a
microscope)
• 5. Definite Chemical Composition (can
a mineral contain rocks…?)
Properties…
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Color
Streak
Luster
Density
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Hardness
Crystal System
Cleavage/Fracture
Special Properties
• Picture, Rock collecting
Egg-shaped rock about
the size of a football…
Geode
o Geodes are formed when water
containing dissolved minerals seeps into
a crack or hollow in a rock
o Crystallization happens lining the inside of
the rock with crystals that are often perfectly
formed.
What is crystallization?
• Geode pictures
• Crystallization – the process by
which atoms are arranged to form
a material with a crystal structure.
 What kind of crystal structures can we have?
• Crystallization picture
• Crystal gardens?
Factors that affect crystal size:
• Amount of gases present
• Chemical composition
• Rate of cooling
Two types of mineral
formation:
• Crystallization of magma and lava
• Crystallization of minerals
dissolved in water
Minerals from magma & lava…
• What’s the difference between
magma and lava?
Magma = below the earth’s surface
Lava = above the earth’s surface
Magma = Underground
• magma
Magma = Underground
Lava = Above Ground
• lava
Lava = Above Ground
Slow Cooling…
• Magma hundreds of miles below the
surface can take many thousands of
years to cool.
• Slow cooling leads to the formation of
very large crystals
– Slow cooling allows atoms to be added
according to a regular pattern
Mineral crystals grow
under a variety of
conditions. Slow cooling
of magma (melted rock)
deep within the Earth
generally leads to a rock
such as granite with
visible crystals of
feldspar, quartz, mica,
amphibole and other
minerals. Water in the
magma can even facilitate
pegmatite formation.
Pegmatite is an igneous
rock composed of mineral
crystals generally with a
diameter of several
centimeters which, on
rare occasions, can be
meters.
• Slow cooled crystals
Fast Cooling…
• Magma close to the surface or lava at
the surface cools much more quickly
• Rapid cooling means the molecules
don’t really have time to form large
crystals
– Do they form a pattern at all?
• Fast cooled crystals
Minerals from solution…
• Solution – a mixture in which one
substance is dissolved in another
• What happens when those compounds
come back out of the solution?
• How would these compounds come out of
solution?
– Minerals can form this way underground and
in bodies of water.
Evaporation…
• Halite
Also…
• Gypsum
• Calcite
Hot water solutions…
• Pure metals that crystallize can dissolve in
hot water solutions and flow through
cracks in rocks to form  veins
• Copper
Also…
• Silver
• Gold
• Vein pictures