Minerals in geology

When magma cools, mineral crystals are formed.. How and where magma cools determine the size of the mineral crystals.. When magma cools slowly beneath the Earth’s crust, large crystals f

Minerals Chapter 3 Glencoe

Section 1 Minerals

Journal Entry

• What is a mineral?

• A mineral is a naturally occurring,

inorganic solid that has a definite chemical composition and crystal structure In order for a substance to be called a mineral, it

must have all of the characteristics

described in this definition

• A mineral must be inorganic, or not formed from living thing or the remains of living things

• A mineral is always a solid Like all solids,

a mineral has a definite volume and shape

Chemical Composition

• A mineral has a definite chemical

composition A mineral may made of a single pure substance, or element, such as gold, copper or sulfur Most minerals are made of two or more elements chemically combined to form a compound

Crystal Structure

• A mineral’s atoms are arranged in a definite pattern repeated over and over again

Atoms not confined, the repeating pattern

of a mineral;s atoms forms a solid called a crystal A crystal has flat sides that meet in sharp edges and corners All minerals have

a characteristic crystal structure

• There are 2500 different kinds of minerals

Crystal Structure

Crystals

Formation and Composition of

Minerals

• Many minerals come from magma, the

molten rock beneath the Earth’s surface When magma cools, mineral crystals are formed How and where magma cools

determine the size of the mineral crystals When magma cools slowly beneath the

Earth’s crust, large crystals form When magma cools rapidly beneath the Earth’s surface, small crystals form

Crystal Formation

• Crystals may also form from compounds

dissolved in a liquid such as water.When

the liquid evaporates, or changes to a gas, it leaves behind the minerals as crystals

Halite, or rock salt, forms in this way

Most Abundant

Elements

• The eight most abundant elements in the

Earth’s crust are oxygen, silicon, aluminum, iron, calcium, sodium, potassium and

magnesium There are about 100 common minerals formed from the eight most

abundant elements.Of these 100, fewer than

20 are widely distributed and make up

almost all the rocks in the Earth’s crust

Rock Forming Mineral Groups

Chemical Classification Mineral Elements

Silicates Feldspar, Pyroxene,

Olivine, Mica, Quartz Silicon, OxygenCarbonates Calcite, Dolomite Calcium Carbonate

Journal Entry

• What properties do we use to identify minerals?

Identifying Minerals

• Minerals have certain physical properties that can be used to identify them, such as color, luster, hardness, streak, density,

crystal shape, and other special properties

mineral azurite is always blue.

• Many minerals come in a variety of colors Some are colorless.Colors can also change

Color

The Many Colors of Quartz

• The luster of a mineral describes the way a mineral reflects light from its surface

Certain minerals have a metallic luster, such

as silver, copper and gold Minerals that do not reflect light have a nonmetallic luster, and are described by terms like glassy,

pearly, dull and silky

Metallic Luster

Non Metallic Luster

• The ability of a mineral to resist being

scratched is known as its hardness

Hardness is one of the most useful

properties for identifying minerals

Friedrich Mohs, a German mineralogist,

worked out a scale of hardness for minerals ranging from 1 to 10 The number one is assigned to the softest mineral, talc and 10

is assigned to the mineral, diamond

Moh’s Scale

1-10

• The color of the powder scraped off a

mineral when it is rubbed against a hard ,

rough surface is called its streak The

streak may be different from the color of the mineral Streak can be observed by rubbing the mineral sample across a piece of

unglazed porcelain, which is called the

streak plate A streak plate has a hardness

slightly less than 7

Streak

• Density is the amount of matter in a given space The density of a mineral is always the same, no matter what the size of the mineral sample

crystal structures: cubic, hexagonal,

orthorhombic, monoclinic, tetragonal and triclinic

Crystal shape

Cleavage and Fracture

• The terms cleavage and fracture are used to describe the way a mineral breaks

Cleavage is the tendency of a mineral to

split along smooth, definite surfaces Some minerals, like halite, break into small cubes Micas cleave along one surface, making

layers of thin sheets Most minerals do not break along smooth lines

Cleavage

Fracture

Special Properties

• Some minerals can be identified by special properties Magnetite is naturally magnetic Fluorite glows under ultraviolet light Halite tastes salty Sulfur smells like rotten eggs Calcite fizzes when hydrochloric acid is

added to Uraninite is radioactive

Journal Entry

• What are some of the uses for minerals?

• Cite specific examples

Minerals and their Gems

• The largest cut from it

is the Great Star of

Africa It weighs 106

grams (530.2 carats)

Useful Gems

• Some gems are useful

• Diamonds are so hard they can scratch

almost any material They are used as

industrial abrasives and cutting tools

• Rubies are used to produce laser lights

• Quartz crystals are used in electronics and timepieces because the quartz will vibrate steadily when exposed to an electric field

Mineral Veins

• Under certain conditions,

metallic elements dissolve

in fluids These fluids

travel through openings or

weak areas in rock and

form deposits

• The mineral deposits left

behind are called vein

mineral deposits.

• Sphalerite, a source of

zinc, is formed this

way.

• Titanium is a lightweight,

durable, metallic element

that comes from mineral

• Two sources are ilmenite

and rutile.

• Titanium is used in

automobile bodies,

aircrafts, eyeglass frames,

wheelchairs and sports

equipment.