What is a Mineral?

What is a mineral?Minerals are naturally occurring,

solid, inorganic compounds or elements.

Did you know…The earth’s crust is composed of about 3000

different minerals!

Some minerals have even helped to shaped civilizations and have boosted the economy of

the countries that they are found in.

Is it a mineral?• Quartz• Salt• Sugar• Coal• Pearl• Diamond

Characteristics of a Mineral

• Naturally occurring and inorganic• Definite crystalline structure• Solid• Specific composition

Crystal• formed by solidification of a

chemical • has a highly

regular atomic structure

So, what is the difference between a rock and a mineral?• Minerals have a unique chemical

composition• Rocks may carry organic remains• Minerals are classified by their chemical

composition, rocks are classified by their process of formation.

• Rocks can be composed of several minerals

Rock-Forming Minerals• Out of the 3000 minerals in the earth’s

crust, only about 30 are common, and only 8-10 of those are referred to as rock-forming minerals.

• The most common of these minerals are Quartz, Feldspar, Mica, Pyroxene, Amphibole, Olivine, Garnet, and Calcite.

How Minerals are Formed• Some minerals are formed from magma.– Cooling and crystallization– Why do different samples of the same mineral

have different size crystals?• Some minerals are formed from solutions.– From supersaturated solutions– From evaporation

Identifying MineralsHardness

Streak TestCleavage

LusterAcid Test

Specific GravityFluorescenceMagnetism

http://www.youtube.com/watch?v=VnM8ebB06MU

Hardness• measure of the

strength of the structure of the mineral relative to the strength of its chemical bonds

Hardness• Moh’s Hardness Scale• Can it scratch glass? Can you scratch it with

your fingernail? What about with a penny?

Where is the mineral on Mohs’ Scale?

Begin by attempting to scratch each mineral with your fingernail. If it scratches using just your

fingernail, its hardness is 1-2.

Where is the mineral on Mohs’ Scale?

If it does not scratch with just your fingernail, try a penny. If it scratches using

the penny, its hardness is 3.

Where is the mineral on Mohs’ Scale?

If it does not scratch with a penny, try gently pulling it across a piece of glass.

If it does not scratch the glass, its hardness is 4-5

Where is the mineral on

Mohs’ Scale?

If it does scratch the glass, its hardness is

6-7.

Streak Test

• color of a mineral in powder form

• determined by streaking across ceramic tile

• May be different from color of actual mineral

Streak Test• What color is it when powdered on a streak

plate?• Gold leaves a yellow streak, Fools Gold leaves

a black streak.

Cleavage• Does it break into flat planes? How many?

Fracture

• Crystal breakage that is not flat – conchoidal (shell-shaped) or uneven

Why?• Question: Why do some minerals break with

flat surfaces and some do not?

• Answer: Some minerals have a regular arrangement of atoms (called crystal structure). This allows them to break with smooth surfaces.

Luster• describes how a mineral reflects light from its

surface

• Glassy (vitreous), metallic, dull, waxy, earthy.

Luster• What does it look

like when the light hits it?

Other tests• Acid Test: Does it fizz when acid is dropped on

it?• Specific gravity: each mineral has a unique

density.• Fluorescence: Does it look fluorescent under a

UV light?• Magnetism: Very few minerals are magnetic.

Other Important Terms to Know

• Opaque: Not allowing light to travel through• Translucent: Allowing some light to travel

through• Transparent: Clear, allowing light to travel

through• Solubility: The property of a substance to

dissolve into another substance. (solvent, solute, solution)

Your Assignment!• Complete the graphic organizer.

1. Define and give other important information regarding each property.

2. Using pictures, illustrate each of the physical characteristics or tests that are used to identify minerals:– Luster– Hardness– Streak– Cleavage

– Acid Test– Specific Gravity– Magnetism– Fluorescence