Mineral Formation

The Earth’s crust is made up of two things:

• Minerals and RocksCoal

Scoria

Gneiss

***You should see lots of different minerals in every single rock

Minerals are individual crystals

of all the same stuff

Rocks are combinations of minerals

What is a mineral?Main Concept: Minerals are the Main Concept: Minerals are the

building blocks of rocks!building blocks of rocks!

There are four There are four mainmain properties properties of a mineral:of a mineral:

a) It must occur naturally (not fake)a) It must occur naturally (not fake)

b) It is made of non-living material (never alive)b) It is made of non-living material (never alive)

c) It has a definite chemical formula (NaCl=salt)c) It has a definite chemical formula (NaCl=salt)

d) It has a crystal structure (OOoo! Precious!)d) It has a crystal structure (OOoo! Precious!)

Examples:

• Amethyst Calcite Garnet

• Galena Gold Pyrite

***Notice how each is one single type of crystal!

Where do minerals come from?

Mineral crystals can form in two main ways:From stuff

dissolved in liquids(Evaporation & Hot Water)

From Cooling molten material

“Intrusive” Cooling:Magma cools slowly

(Long Time = Large Crystals)

“Extrusive” Cooling:Lava cools Fast

(Short Time = Small Crystals)

Minerals & Crystals from

Magma & Lava

•Minerals form from hot magma as it cools inside the crust, or as lava cools

on the surface.

•When these liquids cool to a solid, they form crystals (minerals).

•Size of the crystal depends on time it takes to freeze into a solid.

Minerals Crystal SizeMinerals Crystal Size

RhyoliteGranite

When the hot material cools fast, it has When the hot material cools fast, it has smaller crystal size. When it cools smaller crystal size. When it cools

slowly, it has large crystals.slowly, it has large crystals.

You can’t see many individual crystals in Rhyolite

= cooled very fast

You can see individual crystals

in Granite= cooled slowly

Minerals formed by Evaporation

Some minerals form when solutions/mixtures evaporate: When water evaporates, it leaves behind the

stuff that’s dissolved in it.

The longer it takes to evaporate, the larger the crystal.

i.e. salt & water – ocean, Halite, Gypsum, Calcite.

***All the white stuff = salt mineral crystals that formed when the water of this lake evaporated.

The mineral material was left behind

These salt crystals formed from salt water because as the water

evaporated, the salt wasn’t dissolved anymore. So the

chemical energy in salt takes over and crystals form.

How do we identify Minerals?

We use the different physical and chemical properties of the mineral to identify it from other different minerals

Luster: Describes how light is reflected from a minerals surface.Describes how light is reflected from a minerals surface.

Streak: Is the color of the minerals powder when dragged across a surface.Is the color of the minerals powder when dragged across a surface.

Crystal shape: Different minerals make different crystal shapesDifferent minerals make different crystal shapes

Hardness: Hardness is determined by a “scratch test”.

Color: Every mineral has some natural color…ex: Gold, Blue, Clear…Every mineral has some natural color…ex: Gold, Blue, Clear…

Etc: There are many other types of properties we use but these are the big onesThere are many other types of properties we use but these are the big ones

Special Properties

• Some minerals display strange properties. • These can include: Magnetism, fluorescence, and reactivity.

These minerals glow in the dark.

A black light really brings it out!

The minerals inthis rock react

with acid

Fizzing!

The particles of mineralsof this rock act like magnets