Many types of minerals are found within the earth's crust. A few minerals are elemental. That is, they occur as elements in their uncombined states. Most other minerals consist of a wide variety of naturally occurring ionic compounds, some with simple chemical formulas and others with very complex compositions. Many, but not all, minerals have names that give clues to one or more elements found in their formulas.

In this Internet activity, you make your best guess as to what element might be present in each of the minerals described below. Then go to Minerals by Chemical Composition, find the periodic table, click on that element, and find out the chemical formula of the mineral.

1. Diamond is the hardest mineral of all. Graphite has the same elemental composition.
   
   
2. Because of its high density, barite mud is poured into deep oil wells to buoy up drilling tools.
   
   
3. Hematite is the world's most important source of iron.
   
   
4. Calcite is often found in limestone caverns. Frequently, it is fluorescent.
   
   
5. Because of the beauty of its specimens and its common occurrence, fluorite is one of the most popular minerals among collectors. Both the words fluorine and fluorescence are derived from the name of this mineral.
   
   
6. Halite is also known as rock salt. It's a common kitchen chemical.
   
   
7. A famous mine near the Continental Divide at Climax, Colorado, is a major source of the world's supply of molybdenite.
   
   
8. Although galena's principal constituent is lead, it often is an important source of silver because it contains silver as an impurity.
   
   
9. A variety of uraninite known as pitchblende was once thought to be worthless. With the dawn of the atomic age it became one of the most sought-after minerals in the world.
   
   
10. Quartz contains silicon and is one of the most common minerals. Many beach sands consist of nearly pure quartz.
    
    

Additional Activities

1. Explore Minerals by Chemical Composition to find which pure elements, besides carbon (as diamond and graphite), occur as minerals.
   
   
2. Just what is a mineral, anyway? Check out the various definitions of mineral at the Mineral Database and learn that even the definition of minerals can be very complex.
   
   
3. While you're at it, check out some striking pictures of mineral specimens.