The MIDAS Project: Supported by the Science Education Partnership Award Program of the National Center for Research Resources, National Institutes of Health (Grant No. R25 RR018634)

TEKS: 8.9D, 8.2B Mineral photos from: (except where noted) MINERALS

Minerals are the building blocks that make up rocks. Rocks are made of minerals, but minerals are not the same as rocks Mineral-a naturally formed solid that has a repeating three-dimensional structure. Amethyst from Maine

WHAT IS A MINERAL? Minerals are crystals,which have a repeating inner structure that determines the shape of the crystal. Minerals are inorganic (nonliving). Minerals are formed in nature. Minerals are solid. Diamond from South Africa

TYPES OF MINERALS Minerals are classified by chemical composition. Minerals that contain the elements silicon and oxygen are called silicate minerals. Silicate minerals make up 90% of the Earth’s crust. Wolfenite from Mexico

TYPES OF MINERALS Nonsilicate minerals are made up of other elements such as carbon, sulfur, iron and calcite. These minerals are used in everyday materials such as building materials, medicines, and cosmetics. Sulfur from Italy

IDENTIFYING MINERALS 7 WAYS TO IDENTIFY A MINERAL Barite from Colorado

COLOR 1. Minerals come in many different shades and colors. One mineral can have several colors. Impurities change the color of a mineral. Quartz

Color is not the best way to determine what a mineral is because many minerals are the same color and some minerals come in different colors! Malachite from Arizona Fluorite from Russia Smithsonite from Africa

Calcite comes in many different colors too!

LUSTER 2. Luster- the way the surface of a mineral reflects light. Ex: shiny or dull. Opal from Australia

Silicon Carbide (man made) Talc from Pakistan Sphalerite from Oklahoma Azurite from Arizona Garnet from Afghanistan Minerals have metallic (bright, reflective), submetallic (dull, reflective), or nonmetallic (glassy, silky, resinous, waxy, pearly, and earthy).

STREAK 3. Streak- the color or a mineral in a powdered form. This is not always the same color as the mineral. It tells you the true color of the mineral. Calcite has a white streak. Gold has a golden streak.

CLEAVAGE AND FRACTURE 4. Cleavage- tendency of a mineral to break along flat surfaces. Fracture- tendency of a mineral to break along curved or irregular surfaces. Gold has no cleavage.

This picture shows calcite’s typical rhombohedral cleavage.

HARDNESS 5. The resistance to being scratched is called hardness. Mohs hardness scale is used to compare the hardness of minerals to each other on a scale of 1-10.

Gold has a hardness of on the Mohs Hardness Scale. Mohs Hardness Scale

DENSITY 6. Density- the measure of how much matter there is in a given amount of space. Pure gold is very dense!

SPECIAL PROPERTIES These properties are particular to only a few minerals.

A. Fluorescence – glow under ultraviolet light. Calcite Zircon Fluorite Minerals under daylight and under UV light

B. Chemical reaction – reacts to acids A few drops of acid provides a test for carbonates. This limestone sample bubbles vigorously in response to the acid as CO2 is released.

C. Optical properties – can cause a double image. This picture shows calcite’s optical phenomena known as DOUBLE REFRACTION. - note how the grid pattern is double when viewed through the calcite.

D. Taste – Ex: Halite has a salty taste Never taste an unknown substance! E. Magnetism – natural magnets that attract iron. F. Radioactivity – contain radium or uranium that can be detected by a Geiger counter.

Many minerals are also known as gems. If a mineral is beautiful, durable and rare it is considered a gem.

Beautiful and durable minerals that are not rare are are called semi- precious stones.