Properties of Minerals

What is a Mineral?

Minerals are formed in nature. Minerals are solids.

Minerals have a crystal structure and definite chemical composition.

Minerals are inorganic; not made from a living thing.

• 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:the way a mineral reflects light

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

pearlywaxy metallic metallic, earthy

dull glassy, vitreous resinous, plastic silky, fibrous

Streak• Powder made from rubbing a mineral across

a streak plate; sometimes shows a different color than the mineral appears to be.

• Shows a mineral’s true color

PyriteGalena

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• is the resistance to being scratched• 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

Magnetism Radioactivity Chemical Reaction

FluorescenceSalty Taste

But NEVER taste things in the lab! Double Image