Mineral Formation

Mineral Formation

Inside Earth Chapters 4.2 & 4.3Pages 128-138

How do Minerals Form?

• Recall that minerals form through naturally occurring processes

• There are two main ways:– When melted materials cool– Liquids evaporate.

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 earth-moving equipment to dig a huge pit.

Mining

• Gemstones• Metals• Glass• Cement• Alloy

Uses of Minerals

What to Work On

• Chapter 4 Unit Review on page 142Answer as many questions as you canFor each question, include the number of

the page you found the answer onYou may work in groups

How can we tell one mineral from another?