Introduction To Minerals

Unit Essential Question: How can we use the properties of a mineral to identify it?

Presentation Objectives: § Define a mineral. § Describe the criteria used to define a substance as a mineral. § Explain the difference between a crystal and a crystalline structure. § Describe the two main ways that minerals form.

Remember the Branches?On the first day of school, we discussed the four

branches of Earth Science. What are they?

Geology

MeteorologyOceanographyAstronomy

- The study of the structure and evolution of the earth.

Q1

Structure of the Earth• The Earth has multiple layers, each of which are made

out of different materials. • Inner Core • Outer Core • Mantle • Crust

• Our discussion of geology is going to focus on the crust because that is the layer that is most relevant to our lives. • The Earth’s crust is made out of rocks and minerals, which

are not the same thing.

• Rocks are a combination of different minerals. • There are about 3000 minerals in the Earth’s crust.

Q2 What Is A Mineral?

• A mineral is a naturally occurring, inorganic solid with a specific crystalline structure and a definite chemical composition.

• These are the criteria that must be met to be considered a mineral.

• Some common minerals that you may have seen...

Q3

Criteria 1: Naturally Occurring• To be considered a mineral, nature had to make it.

• CANNOT be man-made.

Sapphire Lab-created Sapphire

Sapphire and Ruby are a form of a mineral known as corundum!

Q4 Criteria 2: Inorganic

• Since minerals are INORGANIC, they aren’t alive and never were alive during any part of their existence.

• Can’t be made from the remains of plants and animals.

Mineral Not A Mineral Not A Mineral

Q5

• In the grocery store, organic refers to food that has been grown and processed without fertilizers, insecticides, artificial coloring, artificial flavorings, or additives.

• In science, organic refers to things that are living or that were once living.

Criteria 3: Solid• A solid is something that has a definite shape and

volume. • Atoms and molecules are close together and move slow.

• There are two types of solids: • Crystalline - atoms are arranged in a geometric

patterns. • Amorphous - atoms are NOT arranged in patterns.

Q6 Criteria 4: Crystalline• Minerals have the atoms arranged in a definite pattern that

is repeated over and over again. • Visible because of the crystals.

• A crystal is a regular geometric solid with smooth surfaces.

• The external expression of a mineral’s atomic structure.

• Minerals can be crystalline but not have crystals.

• Don’t have enough time to form. • Don’t have enough space.

• Interference with other crystals, walls, etc.

Q7

Crystal type is dependent on the chemical composition of the fluid from which it is forming.

Unlimited Space and Time• When crystal growth is not restricted, the resulting

crystal will fall into one of six crystal shapes. • Therefore, we categorize crystals based on their shape

and symmetry. • Known as crystal systems

Cubic

Examples: Fluorite, Halite, Pyrite, & Galena

Q8&9 Crystal Systems Continued...Tetragonal

Examples: Chalcopyrite and Wulfenite

Hexagonal

Examples: Quartz and Beryl (Emerald & Aquamarine)

Q9

Crystal Systems Continued...Orthorhombic

Examples: Sulfur and TopazMonoclinic

Examples: Gypsum, Mica (biotite and muscovite)

Q9 Crystal Systems Continued...Triclinic

Examples: Kyanite, Talc, Turquoise, and Oligoclase

Q9

Criteria 5: Definite Composition• The chemical elements and the amounts of each in a

mineral are unique to that mineral. • Minerals can be single elements.

• Silver • Gold

• Minerals can be compounds. • Galena = PbS • Fluorite = CaF2

Sometimes two minerals have the same chemical composition, but they have a different structure.

DiamondGraphite

Q10 Chemical Composition• While there are about 3000

minerals in the world, they are all made out of the same basic elements.

• The most common elements are:

• O, Si, Al, Fe, Ca, Na, K, Mg

• Since minerals have a definite composition, we can categorize them based on what elements they have in common. • Known as mineral groups.

Q11

Mineral Groups

• About 96% of the minerals in the Earth’s crust are silicates.

• Formed from silica tetrahedron

• Pyramid containing 1 Si atom & 4 O atoms.

Group Name Characteristic Element(s)

Native Single Element (Cu, Ag, Au,)

Silicates Si

Oxides O

Halides F, Cl, I

Sulfides S

Carbonates CO

Sulfates SO

Q11Polymers!

The silicates are polymers of silica tetrahedron.

Single Chain Double Chain

Sheet Framework

Q12

Where Do Minerals Come From?• Cooling of Magma

• Magma is the molten material found beneath the Earth’s surface.

• When it comes to the surface it is called lava.

• As the magma rises toward the surface, the magma begins to cool down. • Rises because it is LESS dense than the surrounding rock. • What happens when a liquid starts to cool?

• Atoms get closer together and they start interacting and bonding.

Crystal size is determined by the rate of cooling. The faster the magma cools, the smaller the crystals.

Q13 Feeling Saturated?• The second way to form minerals is from a saturated

solution. • A solution is a homogeneous mixture, like air.

Q14

• A saturated solution is a one that is full! • A solution in which no more substance can be dissolved.

• Option 2: Let the water evaporate away, and leave the mineral behind.

• There are two options to reach saturation. • Option 1: Add more substance to an already

saturated solution. • Crystals settle out. Known as precipitation.

Resulting minerals are known as evaporites!

Ex: Halite at the Dead Sea