Remember! Rarely is a mineral identified by a single property.

Physical Properties  Color  Streak  Luster  Hardness

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

Color is not a good property to use to identify a mineral? Many minerals have the same color. slate limestone

Color

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

Many minerals have a similar color.

Pure quartz is colorless or white, impurities can make the mineral rose, purple or pink!

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 property that means the way the light bounces off the mineral?

Luster refers to the way a mineral shines in reflected light. Notice the difference between these two minerals?

Luster How minerals reflect light Non- metallic Metallic

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

There are several terms used to describe nonmetallic luster. Examples could be vitreous, like the quartz on the left, or pearly, like the gypsum on the right.

Words that can be used to describe a mineral’s luster? *Glassy *Shiny *Dull*Greasy

Other terms that might be used include greasy, dull, and earthy. Can you tell which of these has an earthy luster and which has a vitreous luster? Earthy Vitreous

Earth Science 2 nd, 3 rd, 4th Monday, October 4, Collected homework assignment from Friday, October 1, 2010 * Read 9.2 {pages } * Outline section Began class notes regarding “Properties used to Identify Minerals” + Read or reread section 9.2, then answer Critical Thinking questions 1-5 and Application 1-4 on page 171.