Mineral Formation

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.

• 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.

Cool Your Crystals

Quartz cools 700 degrees Celsius

• 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.

Sizing Up the Problem

• 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.

Hot Water Solutions

• Minerals also form out of solution when the water evaporates.

• This is what happens when salt water evaporates, leaving only the salt behind.

Formation by Evaporation

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 – looking for ore deposits

1. Strip Mine2. Shaft Mines3. 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.

Mining

TauTona

3.9 kilometers deep

• Open Pit Mines - use giant earthmoving equipment to dig a huge pit.

Mining

• Gemstones• Metals• Glass• Cement• Alloy

Uses of Minerals

How can we tell one mineral from another?