E J C H O N O U R S D A Y 2 0 1 3

ROCKS AND MINERALS

DIFFERENCES BETWEEN ROCKS AND MINERALS

• MINERALS

• Solid formations that occur naturally in the earth

• Have a unique chemical composition

• Defined by its crystalline structure and shape

• ROCKS

• Solid combination of more than one mineral formation

• Can be composed of several minerals

• Can also contain organic remains and mineraloids

• Classified according to the process of its formation

TYPES OF ROCKS

• Igneous

• formed when molten lava solidifies after a volcanic eruption

and is known to be rich in the mineral granite.

• Sedimentary

• formed from deposits of pre-existing rocks, pieces of once-

living organisms or chemical precipitation.

• Metamorphic

• formed by the transformation of one rock type to another,

usually under great heat and pressure.

TYPES OF ROCKS

Igneous

Intrusive

Extrusive

Sedimentary

Clastic

Biologic

Chemical

Metamorphic

Foliated

Non-foliated

IGNEOUS ROCKS

OBSIDIAN

GRANITE

PUMICE

RHYOLITE

ANDESITE

SEDIMENTARY ROCKS

COAL

LIMESTONE

ROCK SALT

SHALE

SANDSTONE

METAMORPHIC ROCKS

MARBLE

QUARTZITE

SLATE

AMPHIBOLITE

GNEISS

MOH’S SCALE OF HARDNESS

• Most common method used to rank minerals

according to hardness.

• Devised by German mineralogist Friedrich Moh in

1812.

• Moh’s hardness refers to a mineral’s ability to resist

abrasion or scratching.

• A mineral with a given hardness rating will scratch

other minerals of the same and lower hardness

ratings.

MOH’S HARDNESS SCALE

Hardness Mineral Description

1 Talc Fingernail scratches it easily.

2 Gypsum Fingernail scratches it.

3 Calcite Copper penny scratches it.

4 Fluorite Steel knife scratches it easily.

5 Apatite Steel knife scratches it.

6 Feldspar Steel knife does not scratch it easily, but scratches glass.

7 Quartz Hardest common mineral. It scratches steel and glass easily.

8 Topaz Harder than any common mineral.

9 Corundum It scratches Topaz.

10 Diamond It is the hardest of all minerals.

IDENTIFYING MINERALS

• Some of the characteristics used to identify minerals

are:

• Colour

• Luster

• Streak

• Cleavage

• Hardness

• Specific Gravity

• Texture

• Crystal

IDENTIFYING MINERALS – COLOUR

• Although commonly used to describe a mineral, it is

not a very good way of identifying a mineral.

• Some minerals are nearly always the same colour,

but many come in a variety of colours.

• Some minerals change colour when the surface is

exposed to moisture and air.

IDENTIFYING MINERALS – LUSTER

• This is the way a mineral reflects light.

Words used to describe luster Example of Mineral

Brilliant Diamond

Dull Kaolinite

Glassy Quartz

Greasy Nepheline

Metallic Pyrite

Pearly Gypsum

Silky Kernite

IDENTIFYING MINERALS – STREAK

• The colour of the powder a mineral produces when

it is dragged across a hard, rough surface.

• For example, pyrite is a brassy, yellow colour, but it

makes a greenish, black streak when rubbed across

a rough surface.

IDENTIFYING MINERALS – CLEAVAGE

• The tendency of minerals to break along definite

planes, creating smooth surfaces.

• For example:

• Galena cleaves into little cubes

• Mica cleaves into thin sheets

• Calcite cleaves into slanting bricks

• Feldspar breaks into little steps

• Quartz cleaves into irregular chunks.

IDENTIFYING MINERALS – SPECIFIC GRAVITY

• The relative weight of a mineral compared to an

equal volume of water. The specific gravity

determines the density of a mineral.

• Two different gems that are the same size can

weigh different amounts.

Specific Gravity Classification of Weight

Less than 3 Light

3 – 5 Average

At least 5 Heavy

IDENTIFYING MINERALS

• Texture

• The physical appearance or character of a rock, such as

grain size, shape and arrangement.

• Crystal

• A solid whose atoms, molecules or ions are packed in a

regularly ordered, repeating pattern. Snowflakes, diamonds,

and common salt are common examples of crystals.

COMMON MINERALS AND THEIR PROPERTIES

Name Colour Streak Luster Hardness Other Properties

Graphite Black Black Metallic 1 Crystals are rare

Mica Colourless White Pearly 2.5-3 Flakes into sheets

Halite Colourless White Glassy 2.5 Salty taste

Galena Gray Gray Metallic 2.5-3 Crystal Cubes

Calcite Colourless White Glassy 3 Crystalline

Magnetite Black Black Dull 5.5-6.5 Magnetic

Pyrite Golden Black Metallic 6-6.5 Looks like gold

Feldspar Various White Glassy 6-6.5 Two cleavages

Quartz Various White Glassy 7 Round fracture

Corundum Gray White Glassy 9 Crystalline

USES OF ROCKS AND MINERALS Rock Use Mineral Use

Basalt Road building

materials

Quartz Glass, electrical components

and optical lenses

Granite Buildings, monuments

and tombstones

Diamond Abrasives

Marble Buildings, tiles Sapphire,

Ruby

Lasers

Obsidian Knives Copper Building construction, electric

cables and wires, switches, alloys

Pumice Scouring, scrubbing

and polishing

materials

Feldspar Glass and ceramic industries,

soaps, cement, fertilizer

Slate Roofs, chalkboards Calcite Cements, mortars, production of

lime

Coal Fuel Graphite Pencil lead, lubricant

Limestone Cement, paper,

petrochemicals,

insecticide, glass

Gold Jewelry, arts, medicine,

currency, scientific and

electronic instruments

BIBLE INCIDENTS IN WHICH A ROCK WAS SIGNIFICANT

Incident Text

Ten Commandments Exodus 31:18

God commands Moses to strike a

rock to provide the Israelites with

water

Numbers 20:2-13

David kills Goliath with a stone 1 Samuel 17

Jesus orders that the stone

covering the tomb of Lazarus be

removed

John 11:38-44

Parable of wise and foolish builders Matthew 7:24-29

Stoning of Stephen Acts 6-7

Woman caught in adultery John 8:1-11

FOUNDATION STONES OF THE NEW JERASULEM

• These can be found in Revelation 21:19,20 and are listed below: • Jasper

• Sapphire

• Chalcedony

• Emerald

• Sardonyx

• Sardius

• Chrysolyte

• Beryl

• Topaz

• Chrysoprasus

• Jacinth

• Amethyst.

SOURCES

• http://en.wikibooks.org/wiki/Adventist_Youth_Honors_Answer_Book/Nature/Rocks_%26_Minerals

• http://www.differencebetween.net/science/difference-between-rocks-and-minerals/

• http://geomaps.wr.usgs.gov/parks/rxmin/rock2.html

• http://geology.com/rocks.shtml

• http://chemistry.about.com/od/geochemistry/a/mohsscale.htm

• http://library.thinkquest.org

• http://www.nma.org/publications/common_minerals.asp

• http://www.coaleducation.org/lessons/wim/20.htm

• http://www.rocksforkids.com/RFK/identification.html