Minerals

MINERALSCh.2

PROPERTIES OF MINERALSCh. 2, Section 1

FIVE PROPERTIES OF MINERALS1. Naturally occurring.

Not man made.

2. Inorganic. Never was living. Not made from any living thing.

3. Solid Has definite volume and shape.

4. Crystal Structure Particles line up in a repeating pattern to form a

crystal shape. Sometimes a microscope is needed to observe

crystals.

5. Definite Chemical Composition Made of definite elements . Can be compounds or pure form minerals.

IDENTIFYING MINERALS Each mineral has its own specific properties

that can be used to identify it. Hardness

How easily the mineral can be scratched. Measured on a scale from 1-10, where 1 is the

softest and 10 is the hardest. Moh’s Scale

Softest: talc, Hardest: diamond. Everything scratches talc, but nothing scratches a

diamond.

Color Easily observed but not always reliable because

many minerals are found in different colors. (Quartz)

IDENTIFYING MINERALS (CONT’D) Streak

A mineral’s powder color. Found by rubbing against a streak plate.

A mineral’s color may vary, but its streak stays the same.

Luster The way a mineral reflects light.

Metallic: shiny, glassy Non-metallic: earthy, waxy, dull

IDENTIFYING MINERALS (CONT’D)

Density: Mass in a given space or mass per unit volume Never changes in a given mineral. Mineral is weighed to determine mass. Then,

mineral is placed in water to see how much water it displaces: volume. Mass is divided by volume to determine density.

Crystal Systems Each mineral has its own particular crystal

structure. 6 systems: cubic, hexagonal, tetragonal,

orthorhombic, monoclinic, and triclinic

IDENTIFYING MINERALS (CONT’D)

Cleavage and Fracture Way a mineral breaks. Cleavage splits evenly along flat surfaces. Fracture breaks unevenly.

SPECIAL PROPERTIES

Not all minerals have special properties. Include magnetism, fluorescence, reaction to

acids, electrical

HOW MINERALS FORMCh.2, Section 2

PROCESSES THAT FORM MINERALS

Form in 3 basic ways:1. Crystallization from melted materials.2. Minerals formed by hot water solutions.3. Minerals formed by evaporation.

CRYSTALLIZATION FROM MELTED MATERIALS

1. Magma cooling inside crust.2. Lava cooling outside of the crust.

Crystal size determined by 3 factors:1. Rate at which magma cools.

Slow cooling results in large crystals. Fast cooling results in smaller crystals

(sometimes not visible at all).

2. Amount of gas magma contains.3. Chemical composition of the magma.

MINERALS FORMED BY HOT WATER SOLUTIONS

Elements that make up a mineral dissolve in water heated by magma deep beneath the Earth’s surface.

Dissolved minerals form solutions. Hot water begins to cool, elements and

compounds leave the solution and crystallize as minerals.

Pure metals that crystallize underground often form veins.

MINERALS FORMED BY EVAPORATION

When solutions evaporate, minerals can form. Ex. Salt water. Water evaporates, leaving salt

crystals in the bottom of the container. Halite formed by evaporation of ancient seas.

WHERE MINERALS ARE FOUND

Crust is made up of common minerals. Rare minerals found near volcanic areas or

areas of mountain building. (Cu found near Andes Mountains in Chile)

MINERAL RESOURCESCh.2, Section 3

USES OF MINERALS

Sources for metals, gemstones, and other materials used to make many products.

ORES

Rock that contains metal or an economically useful mineral.

Most metals do not occur in a pure form. Minerals have to be separated from the ore.

PROSPECTING

Prospectors search for ore deposits. Geologists look for certain features on Earth.

Observe rocks on land. Examine plants growing in an area. Test stream water for presence of chemicals.

Geologists also examine Earth’s interior for ores. Set off explosions below ground. Explosions create shock waves. Echoes of shock waves used to map location,

size, and shape of ore deposit.

MINING

Strip Mines Earthmoving equipment scrapes away soil to

expose ore. Open-pit Mining

Earthmoving equipment dig pits to remove ore deposits.

Shaft Mines Have a network of tunnels that follow veins of

the ore.

SMELTING

After miners remove the ore from the mine, the use the process of smelting to remove the metal from the ore.

After smelting, additional processes can be carried out to increase the value of the metal. Impurities can be removed to make the metal harder. (Ex. Iron becomes steel)

Alloys, mixtures of 2 or more metals, are created to insure that the metal has desirable properties. (strength)