There are about 3,000 known There are about 3,000 known minerals, only about 30 are minerals, only about 30 are

common.common.

The most common are The most common are quartz,feldspar,mica, and calcite.quartz,feldspar,mica, and calcite.

These minerals make up most These minerals make up most of the rocks found in the of the rocks found in the

Earth’s crust.Earth’s crust.

Most of the Earth’s crust is Most of the Earth’s crust is made up of feldspar, followed made up of feldspar, followed

by quartz and mica.by quartz and mica.

So what is a mineral?So what is a mineral?

What are the What are the characteristics of all characteristics of all

minerals?minerals?

What is a mineral?What is a mineral?

Mineral- A mineral is a naturally formed, Mineral- A mineral is a naturally formed, inorganic solid with a crystalline inorganic solid with a crystalline structure.structure.

Rocks are actually made of many Rocks are actually made of many minerals but minerals are not made of minerals but minerals are not made of rocks.rocks.

1. A mineral occurs naturally.1. A mineral occurs naturally.

2. A mineral is solid.2. A mineral is solid.

3. A mineral has a definite 3. A mineral has a definite chemical composition.chemical composition.

4. A mineral’s atoms are 4. A mineral’s atoms are arranged in an orderly pattern.arranged in an orderly pattern.

5. A mineral is inorganic (was 5. A mineral is inorganic (was never alive)never alive)

To be able to identify these and To be able to identify these and other minerals, we need to look other minerals, we need to look

at the at the properties properties used to used to separate and distinguish these separate and distinguish these

minerals.minerals.

Remember!:Remember!:

Rarely is a mineral identified Rarely is a mineral identified by a single property.by a single property.

These properties need to be These properties need to be considered together to considered together to

correctly identify a mineral.correctly identify a mineral.

Mineral propertiesMineral properties►ColorColor►LusterLuster►Habit (Shape)Habit (Shape)►Cleavage & FractureCleavage & Fracture►StreakStreak►HardnessHardness►OtherOther

Color is the most easily Color is the most easily observed mineral property observed mineral property

and the and the leastleast useful! useful!

Many minerals have a similar Many minerals have a similar color.color.

Many minerals can turn colors Many minerals can turn colors due to impurities. They may due to impurities. They may

also have a mottled appearance also have a mottled appearance or wavy appearance.or wavy appearance.

For example, pure quartz is For example, pure quartz is colorless or white, colorless or white,

impurities can make the impurities can make the mineral rose, purple or pink!mineral rose, purple or pink!

Luster refers to the Luster refers to the way a mineral way a mineral shines in reflected lightshines in reflected light..

Notice the difference between Notice the difference between these two minerals?these two minerals?

The mineral on the left has a The mineral on the left has a metallic lustermetallic luster, the one on , the one on

the right, a the right, a nonmetallic nonmetallic lusterluster..

Certain minerals have a Certain minerals have a metallicmetallic luster, luster, such as silver, copper and gold. such as silver, copper and gold.

Minerals that do not reflect light have Minerals that do not reflect light have a a nonmetallicnonmetallic luster, and are described luster, and are described by terms like glassy, pearly, dull and by terms like glassy, pearly, dull and

silky.silky.

Other terms that might be used Other terms that might be used include include greasy, dull, greasy, dull, and and earthyearthy..

StreakStreak of a mineral is the color of a mineral is the color of its powder when rubbed on of its powder when rubbed on

an unglazed white tile.an unglazed white tile.

The streak is often not the same The streak is often not the same color as the mineral. color as the mineral.

A minerals color may vary, but A minerals color may vary, but the streak rarely will!the streak rarely will!

The The cleavage cleavage of a mineral is of a mineral is how it breaks.how it breaks.

MicaMica is probably the best is probably the best example as it splits into thin example as it splits into thin sheets. It is said to have one sheets. It is said to have one

perfect cleavage.perfect cleavage.

FeldsparFeldspar splits readily in two splits readily in two directions, always at or near directions, always at or near

right angles.right angles.

Cleavage & FractureCleavage & Fracture

Best identified on a fracture surface

How resistant the mineral is to being How resistant the mineral is to being scratched.scratched.

Diamond is the hardest of all minerals, and Diamond is the hardest of all minerals, and talc is the softest.talc is the softest.

Friedrich Friedrich MohsMohs devised a devised a hardness scale. hardness scale.

In this scale, ten well known In this scale, ten well known minerals are given numbers minerals are given numbers

from one to ten.from one to ten.

Talc Talc (left) is the softest and has a (left) is the softest and has a hardness of 1. A soft pencil lead hardness of 1. A soft pencil lead

will scratch talc.will scratch talc.GypsumGypsum is a bit harder and has a is a bit harder and has a

hardness of 2. A fingernail hardness of 2. A fingernail scratches gypsum.scratches gypsum.

CalciteCalcite (left) has a hardness of 3 (left) has a hardness of 3 and a copper penny just and a copper penny just

scratches it.scratches it.

DiamondDiamond with its hardness of 10 with its hardness of 10 can easily scratch the rest of the can easily scratch the rest of the

minerals. minerals.

► Moh's Hardness ScaleMoh's Hardness Scale► HardnessHardness MineralMineral DescriptionDescription► 11 TalcTalc Fingernail scratches it easily.Fingernail scratches it easily.► 22 GypsumGypsum Fingernail scratches it.Fingernail scratches it.► 33 CalciteCalcite Copper penny scratches it.Copper penny scratches it.► 44 FluoriteFluorite Steel knife scratches it easily.Steel knife scratches it easily.► 55 ApatiteApatite Steel knife scratches it.Steel knife scratches it.► 66 FeldsparFeldspar Steel knife does not scratch it Steel knife does not scratch it

easily, but scratches glass.easily, but scratches glass.► 77 QuartzQuartz Hardest common mineral. It Hardest common mineral. It

scratches steel and glass easily.scratches steel and glass easily.► 88 TopazTopaz Harder than any common Harder than any common

mineral.mineral.► 99 CorundumCorundum It scratches Topaz.It scratches Topaz.► 1010 DiamondDiamond It is the hardest of all minerals.It is the hardest of all minerals.

Would a fingernail scratch calcite?

NO

Would a steel nail scratch orthoclase?

NO

Would a copper penny scratch talc?

YES

Would a copper penny scratch fluorite?

NO

Would a fingernail scratch gypsum?

YES

Crystal shapeCrystal shape can be a useful can be a useful property to identify minerals if property to identify minerals if the minerals have had the time the minerals have had the time

and space to form crystals. and space to form crystals. Most mineral grains that are Most mineral grains that are

found in rocks, lack the room to found in rocks, lack the room to grow.grow.

Malleable

Magnetic

Radioactive

Flourescence

Taste

HaliteHalite (rock salt) (rock salt) can be identified can be identified

by its taste.by its taste.

This practice is This practice is not not

recommended!recommended!

This is the state of This is the state of glowing while glowing while

under a ultraviolet under a ultraviolet light.light.

Some minerals Some minerals even glow once even glow once

the light is turned the light is turned off!off!

Some minerals, Some minerals, such as this such as this

uraniniteuraninite, are , are radioactive.radioactive.

They give off They give off subatomic subatomic

particles that will particles that will activate a activate a Geiger Geiger

countercounter..

Some minerals Some minerals that contain that contain

Iron, are Iron, are magnetic and magnetic and can be picked can be picked

up by a up by a magnet.magnet.