Properties of Minerals

Minerals• Minerals occur naturally - they are not man-made. They grow, but they do not have life.

Each kind of mineral has a special color, crystal shape, luster, hardness, and even its own way of splitting or breaking apart. A geologist - a scientist who studies the Earth and its rocks - will study all those things to determine what type of mineral they have found.

• People do not make minerals. They are formed within the Earth's mantle, within the Earth's crust, or on the surface of the Earth. Strong heat and pressure form minerals in much the same way as rocks are formed.

• Minerals make up rocks. Some rocks have only one mineral in them. Marble, from which statues are carved, has only one mineral called calcite [CAL-site]. Other rocks are made up of several different minerals.

• You do not have to go into a cave or dig in the ground to find minerals. Your home is full of them! Your toothpaste contains a mineral called fluorite. Your bath powder contains talc. Your clock radio contains the minerals copper, gold, quartz, and cassiterite [kuh-SIT-uh-right] - the ore of tin. Your pencils contain graphite. The salt you use to season your food is a mineral!

What is a Mineral?

Minerals are formed in nature. Minerals are solids.

Minerals have a crystalline, geometric structure.

Minerals are inorganic; not made from a living thing.

Major Properties

• Color: come in many different colors• Luster: the way a surface reflects light• Streak: the color of a mineral in powder form• Cleavage: the tendency of a mineral to break

along flat surfaces• Fracture: the tendency of a mineral to break

unevenly along curved or irregular surfaces• Hardness: a mineral’s resistance to being

scratched• Density: ratio of mass to volume

• Impurities and other factors can give minerals their color

These minerals are ALL forms of quartz! Color is not a reliable way to describe minerals.

• Exposure to weather or chemicals may change the color of minerals.

Color is not a reliable property to use in the identification of minerals!

Oxidation turns iron from silver to black to red!

Pyrite turns grey and black.

Copper turns green!

Amethyst$68.00

Tanzanite$720.00

Sapphire$500.00

Diamond$3,000.00

Moissanite$349.oo

REAL Gold

Luster• plastic, dull, metallic, waxy, pearly, glassy, silky

pearlywaxy metallic metallic

dull glassy, vitreous resinous, plastic silky, fibrous

Streak• Powder made from rubbing a mineral across a

streak plate

Pyrite

Galena

Hematite

Cleavage• Minerals that break along even lines have

cleavage.

Types of Cleavage

Fracture• break along curved or irregular surfaces

Conchoidal, “shell-shaped” fibrous

irregular

Hardness

• Hardness can be measured using a scratch test:• using Mohs Hardness Scale, which compares

minerals to each other• using common items such as a fingernail,

copper penny, steel knife blade, glass

A fingernail can scratch talc. Quartz can scratch glass, but fluorite cannot.

Density

• How much matter there is in a given space

• Density = Mass divided by Volume

volume mass

Special Properties

MagnetismRadioactivity Chemical Reaction

Fluorescence

Salty TasteBut NEVER taste things in the lab! Double Image

Economic Importance of Minerals

• Minerals are in many things we see and use everyday such as; bricks, glass, cement, plaster, iron, gold

Every American Requires 40,000 Pounds of New Minerals per Year

• at this level of consumption the average newborn infant will need a lifetime supply of:-795 lbs of lead (car batteries, electric components)-757 lbs of zinc (to make brass, rubber, paints)-1500lbs of copper (electrical motors, wirings-3593 lbs aluminum (soda cans, aircraft)-32,700 lbs of iron (kitchen utensils, automobiles, buildings)-28,213 lbs of salt (cooking, detergents)-1,238,101 lbs of stone, sand, gravel, cement (roads, homes, etc.)