Whether we realize it or not, everyone in the world relies on minerals. They are in the food we eat; the homes we live in; and the video game systems, computers, and cellular phones we use every day! So, what are minerals? And, why is Dr. Mike Wise traveling the world researching, studying, and trying to find them?

Minerals are naturally occurring, solid substances. They form directly from geologic sources that were not once living. To date, more than 4,000 minerals have been discovered! And new ones are found every year. Rocks, on the other hand, are substances made from a variety of materials, including minerals, fragments of other rocks, plants, and even the remains of animals.

Each mineral can be identified using a single chemical formula. Whether the mineral is made of a single type of atom or combination of atoms, called molecules, the formula is constant. Some minerals can share the same chemical composition. Graphite and diamond, for example, are both made of carbon (C). Groups of minerals can contain very similar formulas, varying slightly between the minerals. The Feldspars group has variations containing potassium (KAlSi₃O₈), sodium (NaAlSi₃O₈), and calcium (CaAl₂Si₂O₈).

All minerals form crystals, which are organized and repeating atoms or molecules joined together. This organized repeating pattern is called a crystal structure. You can see and taste mineral crystals every time you put salt on your food. Use a hand lens to take a closer look at a few salt crystals. What do you notice?

What Makes a Mineral?

In order to be considered a mineral, five specific criteria must be met.

Occurs Naturally A mineral cannot be a human-made substance, such as plastic. Crystalline solids produced in a lab, such as diamonds, are formed by different processes than how they form naturally. These human-made crystals are not considered minerals.

Formed Directly from Geologic Sources Minerals are formed directly from geologic sources, such as molten rock or the evaporation of salt water. Minerals do not form directly from biological sources. Pearls created by oysters and coal created from the remains of plants are not considered minerals.

Solid A mineral must have a definite shape and volume. For example, water is not a mineral in its liquid form. However, in a naturally-made and solid form, ice is a mineral.

Definite Chemical Composition Minerals have a specific chemical formula. For example, the chemical formula for quartz is SiO₂. Amethyst, citrine, jasper, and agate are all varieties of quartz; therefore, they all have the same base chemical composition with only slight impurities that affect their color.

Forms a Crystal Structure The shape of the crystal structure is reflected by the repeating pattern of atoms or molecules. Glass might appear to be a mineral, but is not because when it forms, the atoms bond in a random manner rather than a repeating structure.

Identifying Minerals

When geologists, like Dr. Wise, are in the field or in the lab, they occasionally stumble upon an unknown sample. After examining it with an eye loop or magnifying glass, the geologist will try to identify it. Establishing the identity of a sample requires testing the sample in some key ways.

Each mineral has a distinct set of physical properties associated with it. These properties include color, crystal structure, streak, luster, density, hardness, conductivity, and cleavage. Each physical property provides a clue about what mineral it could be. Together, these properties can be used to help identify minerals you see and collect in the field.

Mineralogists have also developed specific methods for classifying minerals. The Dana Classification is the system used most often. It was published in the mid-1800s by James Dana. In 1997, the New Dana Classification system was implemented. The New Dana Classification expanded the original eight classes of minerals to 78 classes.