1. A mineral occurs naturally

2. A mineral is solid (definite shape & volume). It’s a crystalline structure.

3. A mineral has a definite chemical composition (combines several atoms).

4. A mineral ’ s atoms are arranged in repeating patterns (Crystal).

5. A mineral is inorganic (was never alive)

Magma ► Minerals can form from the cooling of magma. ► Magma is molten material found beneath Earth’s surface.

Minerals from Solution ► Minerals can form from a supersaturated solution. ► For example: Gypsum deposits can form from the evaporation of water.

Of the almost 4000 known minerals, only about 30 are common. The most common are quartz,feldspar,mica, and calcite.

These rock forming minerals make up most of the rocks found in the Earth ’ s crust.

Silicates ► Minerals that contain both O and Si and one or more other elements are known as silicates. ► Make up 96% of the minerals in the Earth’s crust. ► Example: Feldspar and Quartz

Carbonates ► Minerals composed of one or more metallic elements with the carbonate compound CO 3. ► Examples: Calcite, dolomite, and rhodochrosite.

To be able to identify these and other minerals, we need to look at the properties used to separate and distinguish these minerals.

Oxides ► Compounds of oxygen and a metal.

Minerals are identified by several properties!

Color is the most easily observed mineral property and the least useful!

Some exceptions to the color rule would be cinnabar, which is always red, and malachite, which is green.

Discuss the following with a neighbor! How many of the characteristics of minerals can you name? Why isn ’ t color a very good property to identify most minerals?

Luster refers to the way a mineral shines in reflected light.

The mineral on the left has a metallic luster, the one on the right, a nonmetallic luster.

Streak of a mineral is the color of its powder when rubbed on an unglazed white tile.

The streak is often not the same color as the mineral. A minerals color may vary, but the streak rarely will!

The cleavage of a mineral is its tendency to split easily or to separate along flat surfaces. Cleavage can even be observed on tiny mineral grains making it a very useful property!

Mica is probably the best example as it splits into thin sheets. It is said to have one perfect cleavage.

Feldspar splits readily in two directions, always at or near right angles.

Not all minerals show cleavage. Those that don ’ t break along cleavage surfaces are said to have fracture.

Discuss the following with a neighbor! There are four common minerals, how many can you name? Of the four common minerals, which one makes up over 60% of the Earth ’ s crust?

The hardness of a mineral is its resistance to being scratched. Diamond is the hardest of all minerals, and talc is the softest.

Friedrich Mohs devised a hardness scale. In this scale, ten well known minerals are given numbers from one to ten. Lets take a look at the ten minerals used and some of the simple tests.

The Mohs Hardness scale ranks from most likely to be scratched (1) to least likely to be scratched (10).

Crystal shape can be a useful property to identify minerals if the minerals have had the time and space to form crystals. Most mineral grains that are found in rocks, lack the room to grow.

Specific gravity tells you how many times as dense as water the mineral is. Pure gold can have a specific gravity as high as 19.3!

Calcite is calcium carbonate, CaCO 3. If a drop of weak hydrochloric acid is placed on calcite, the acid bubbles as carbon dioxide is released.

Minerals that can be hammered thin or shaped are said to show these properties. Can you think of a mineral that might be shaped or hammered?

Gold would be a perfect example!

Halite (rock salt) can be identified by its taste. This practice is not recommended!

Ores ► A mineral is an ore if it contains a useful substance that can be mined at a profit. ► Look around the room, are any items made of iron? If so, their original source may have been hematite.

Items that contain iron

Ores Continued… ► Ores located deep with Earth’s crust are removed by underground mining. ► Ores that are near Earth’s surface are obtained from large, open-pit mines.

Gems ► What makes a ruby more valuable than mica? ► Rubies are much rarer and more visually pleasing than mica. ► Rubies thus are considered GEMS. ► Gems are valuable minerals that are prized for their rarity and beauty.

Examples of Gems Diamonds Emeralds