The Identification of Minerals

Did you know there are over 3,800 known minerals on Earth? Did you know there are scientists who can identify almost any mineral set in front of them? Have you ever wondered how these scientists do this? Maybe they memorize them all at Earth Science school. Talk about creating memory devices!

I became interested in how scientists do this so I did a little research. It turns out, there are basically five tests that can be used to identify a mineral. These five tests are fairly simple and almost anyone can do them. For those of you who are armchair minerologist I humbly present The Identification of Minerals.

The first test is hardness of the mineral. Hardness is a mineral's resistance to scratching. A scale, known as the Mohs Hardness Scale, is used to enumerate hardness. The numbers one through ten are used, with one being the softest of minerals and ten being the hardest.

As I said, these tests are simple. To determine hardness all that is needed is a fingernail and a piece of glass. It turns out that a fingernail has a hardness of roughly two while glass is right around five. This means that a mineral that is scratched by your fingernail has a hardness of two or less. A mineral that scratches glass has a hardness of more than five. If neither condition is true, the mineral's hardness is between three and five. In this way, you can determine the range of hardness your mineral is in.

The next test used in identifying minerals is luster. Luster is determined by the amount of light a mineral reflects. Luster is divided into metallic and nonmetallic. These are just as they sound, one looks like metal and the other does not. There are very good examples in the links. There are several subcategories under these categories, including bright or dull, soapy or earthy, greasy or vitreous. The links provided below can help define these terms and show how they are used in the identification of minerals. Usually, just knowing a mineral has a metallic luster or not is, in conjuction with the other tests, enough to identify a mineral.

Sometimes color is also helpful is the identification of minerals. You must be cautious with color, however, because it is not very reliable. For example, while sulfur is always yellow, quartz varies. It is easy to mistake one for the other on the basis of color alone.

Fortunately, streak is a very reliable source of identification. Streak is the color a mineral leaves when it is rubbed across an unglazed porcelain streak plate. The streak is the true color of the mineral.

The final element in mineral identification is cleavage and fracture. Cleavage and fracture are hard to understand. Basically, cleavage and fracture are the way a mineral breaks. Cleavage has occurred only if there are smooth flat surfaces on the mineral. Cleavage causes light to be reflected off its surface. This is not to be confused with luster. Cleavage and luster are not the same thing.

The easiest definition of fracture is the absence of cleavage. It usually results in uneven and jagged surfaces. Again, the links below are wonderful resources for any questions you may have.

These five tests can be used together to identify a mineral. With the use of a mineral wheel, almost any mineral can be identified fairly easily. A mineral wheel shows the elimination of characteristics until only one mineral is left. It is like using the process of elmination to determine a mineral. Now, all armchair mineralologists can figure out the name of that mineral that I know is driving you crazy. Good luck and happy identifying!