Mineral Formation
Pages 56-66
How do Minerals Form?
• Recall that minerals form through
naturally occurring processes
• There are two main ways:
– When melted materials cool
– Dissolved in water.
Cool Your Crystals
• Minerals form as
liquid rock cools,
either inside the
crust or outside
– Magma: molten
material below the
crust
– Lava : magma that
reaches the surface.
Cool Your Crystals
• Deeper in the
earth, magma
cools slowly. Slow
cooling means
bigger crystals.
Olivine cools at 1200 degrees Celsius
Cool Your Crystals
• Faster cooling
occurs closer to or
at the surface. This
means smaller
crystals.
Quartz cools 700 degrees Celsius
Sizing Up the Problem
• Problem: How does the cooling
temperature affect crystal size?
• Hypothesis:
Minerals that cool at a higher temperature
have larger crystals.
Minerals that cool at a lower temperature
have smaller crystals.
Hot Water Solutions
• Some elements dissolve
into hot water below
Earth’s surface
• This creates a solution:
– A mixture in which one
substances dissolves in
another.
Hot Water Solutions
• Heated water solution
races upwards through
cracks in the rock
• In the cracks, they
crystallize to form veins:
-- Narrow channels or
slabs of minerals that
are very different from
the surrounding rock.
Formation by Evaporation
• Minerals also form out
of solution when the
water evaporates.
• This is what happens
when salt water
evaporates, leaving only
the salt behind.
Mineral Deposits
• Ore: a mineral that contains a metal or
economically useful mineral.
• Prospecting: searching for an ore deposit.
– Geologists use features and rocks on the
surface.
Mining
• Mining – looking for
ore deposits
1. Strip Mine
2. Shaft Mines
3. Open Pit Mines
Mining
• Strip Mine
– Earth moving equipment scrapes
away soil to expose ore.
Mining
• Shaft Mines network of tunnels
that extend deep
into the ground
following the veins
of ores.
TauTona
3.9 kilometers deep
Mining
• Open Pit Mines - use giant earthmoving
equipment to dig a huge pit.
Uses of Minerals
• Gemstones
• Metals
• Glass
• Cement
• Alloy
How can we tell one mineral from another?