Mineral Properties

Key Concepts A pure substance, such as a mineral, can be identified from observations and tests performed to determine its physical properties. These properties are based on the unique structure of the substance. Minerals are crystals that form naturally in the Earth. They have characteristic properties, such as color, hardness, and a crystalline shape. Rocks are made of minerals.

Vocabulary Crystalline structure – the regular pattern of atoms, molecules or ions in a crystal. Geologist – scientist who studies the Earth and the changes that take place on and beneath the surface

Vocabulary Mineral – a naturally occurring solid material that has a specific chemical composition and crystal form and characteristic physical properties. There are about 3,500 different minerals. Rock – a naturally occurring solid substance composed of one or more minerals.

Minerals/4 Characteristics Forms in nature Is a solid Has a definite chemical make-up Has a crystal structure

Minerals Form In Nature Formed by natural processes. Are inorganic which means they are made of non-living materials found naturally on earth.

A mineral has a definite volume and a rigid shape. Minerals are Solids A mineral has a definite volume and a rigid shape. Volume refers to the amount of space an object takes up

Definite Chemical Make-up Every mineral consists of a specific combination of atoms of certain elements. The types of atoms that make up a mineral are part of what makes the mineral unique. The way in which the atoms are bonded, or joined together, is also important. Many properties of minerals are related to how strong or weak the bonds are.

Crystal Structure The way the atoms are arranged in an orderly, repeating three-dimensional pattern. Each mineral has its own type of crystal structure. Minerals can have the same chemical compound/same type of atoms, but the way the atoms are arranged is different. Diamonds and graphite are made of the same element, carbon, but the arrangement of these carbon atoms is different.

Mineral Properties Minerals have characteristic properties that are used to identify them: 1. color 5. Fracture 2. luster 6. Density 3. transparency 7. crystalline structure 4. streak color 8. crystal habit (shape)

Look at the following minerals Look at the following minerals. Which do you think are the same types of minerals and which do you think are different?

Haha! Tricked you! These are all… …the same type of mineral! They are examples of quartz!!

Why Is It So Difficult to Identify Minerals? There are over 3000 types of minerals in the Earth’s crust As you could see with the quartz, often times even the same kind of minerals can look very different Therefore, geologists (scientists who study minerals and rocks) often use several different tests to determine type of a mineral they have found!

Color Color is obviously one of the most noticeable characteristics of a mineral, but it also the least reliable of all the characteristics The color of a mineral is often caused by tiny amounts of other elements or compounds inside For example, what people call amethyst is actually just quartz with iron in it!

Luster The way that a mineral reflects light from its surface is its luster The two types of luster are: - metallic - nonmetallic Metallic Luster

Texture Texture describes how a mineral feels to the touch. Minerals can range anywhere between glassy feeling, rough feeling, greasy feeling, and even soapy feeling! Talc has a soapy texture. Fluorite has a glassy texture.

Streak When a mineral is rubbed against a tile, it will leave behind a colored powdered streak on the tile Sometimes a mineral’s streak does not match the mineral’s external color For example, one way to tell the difference between pyrite (Fool’s gold) and real gold is by streak. Pyrite leaves a greenish-black streak while real gold leaves a yellow streak.

Hardness is a measure of how easily a mineral can be scratched Associations and Uses 1 Talc Talcum powder. 2 Gypsum Plaster of paris. Gypsum is formed when seawater evaporates from the Earth’s surface. 3 Calcite Limestone and most shells contain calcite. 4 Fluorite Fluorine in fluorite prevents tooth decay. 5 Apatite When you are hungry you have a big "appetite". 6 Orthoclase Orthoclase is a feldspar, and in German, "feld" means "field". 7 Quartz   8 Topaz The November birthstone. Emerald and aquamarine are varieties of beryl with a hardness of 8. 9 Corundum Sapphire and ruby are varieties of corundum. Twice as hard as topaz. 10 Diamond Used in jewelry and cutting tools. Four times as hard as corundum. Hardness is a measure of how easily a mineral can be scratched Geologists use Mohs scale to give minerals their hardness ratings

Cleavage and Fracture The pattern of atoms will determine how a mineral will break A mineral that breaks relatively easily and evenly at angles is said to have cleavage Minerals that break with rough or jagged edges are said to have fracture

Some Other Special Properties Some minerals have unique properties For example, Iceland spar can create double images Some minerals react with hydrochloric acid and release carbon dioxide (bubbles)