Mineral Properties

LOLLIPOP, LOLLIPOP. . . Imagine that you have just entered the store of your dreams. It is filled with all kinds of sweet, colorful candy. You immediately spot a very large display of lollipops. You have a quarter and you decide to buy one. Your favorite flavor is watermelon. You ask the lady behind the counter for a watermelon lollipop. The lady is confused. She has just started working there that day, and there are no labels on the lollipops. She does not know which of the many different lollipops is watermelon. YOU'RE THE SCIENTIST! Think about the above problem. On a sheet of paper explain how you could solve the problem of determining which sucker is the watermelon flavored lollipop?

NARROWING THE FIELD! Perhaps the first thing you would do, would be to look at the color of the lollipops. You might be able to eliminate some of the lollipops based on color. For example, black lollipops are probably licorice flavored. Yellow lollipops might be lemon flavored. Watermelon colors are usually a pink, red or green color. After looking at the lollipops, you decide it is probably one of four that you picked out based on the color. What could you do to find out which of the four lollipops is watermelon? Your next step might be to smell each of the lollipops. Red lollipops might also be cinnamon flavored, and cinnamon flavoring has a very distinct smell. By the process of elimination you have been able to narrow your lollipop search down to two lollipops. Are there other ways to identify which lollipop is the watermelon flavored candy? There sure are, and the nice lady behind the counter said to go ahead and taste the pink one. She said if it wasn't watermelon, she would let you have both of the lollipops anyway.

COMMON SENSE! You are probably wondering what the above story has to do with rocks and minerals. It is really quite simple. In the story, you identified the watermelon lollipop by using your senses. You first looked at the lollipop's appearance. Next, you smelled the lollipops. Finally, you tasted the lollipops. You can also identify minerals by their physical properties. You can learn to identify many minerals by their appearance. Other properties used to identify minerals include smell, feel, and how a mineral might sound when it is tapped.

After practicing a bit, you should be able to identify some minerals using the above tools. But these tests are not always reliable. The mineral quartz, for example, comes in a great variety of colors. There are other tests that you can perform to correctly identify minerals.

HARDNESS One physical property of minerals is their hardness. Some minerals such as talc are very soft and can be scratched with a fingernail. You already know that diamond is very hard and nothing can scratch it. Other minerals fall somewhere in between. The scale on the right was invented by a scientist named Moh. He made this scale to help people determine the hardness of minerals. Every mineral has a specific hardness.

MOH'S SCALE OF HARDNESS 1. TALC - VERY SOFT 6. ORTHOCLASE 2. GYPSUM 7. QUARTZ 3. CALCITE 8. TOPAZ 4. FLUORITE 9. CORUNDUM 5. APATITE 10. DIAMOND - VERY HARD FINGERNAIL = 2.5 PENNY = 3 STEEL NAIL = 5.5 GLASS = 6

STREAK When you rub a mineral against the back side of a porcelain tile it will leave a streak. Sometimes the streak is the same color as the mineral. Sometimes the streak is a different color. And sometimes there is no streak at all. Different minerals have different streaks.

TEST TIME! There are several other tests that can help to identify minerals. Some minerals will fizz if you put vinegar, which is an acid, on them. Sulfur can be identified by its rotten egg smell, and halite (rock salt) oddly enough, tastes like salt. There are minerals that glow under ultraviolet light. Some minerals are more "hefty" than others. All of these physical properties are useful in mineral identification.

FIND IT! Use the Internet to find two other tests that can be used to identify minerals. Write a paragraph about these methods.

IDENTIFY IT! Collect several rocks or have your teacher provide you with some samples. Use a mineral classification key to identify the samples. Be sure to record your test results to explain your identification methods. MAKE IT! Make a mineral "ABC" book. Find information on a mineral that begins with the letter "A." On a sheet of paper, cut out or draw a picture of the mineral. Record the following information about the mineral: Name of mineral Composition (Elements from which it is made) Physical properties (Hardness, streak, etc.) Uses Other interesting facts about the mineral Repeat this process using all letters of the alphabet. When you have completed the above steps, make a cover sheet and bind the papers together.
GO THERE! By clicking on any of the letters above, you can find more information about mineral identification.