Not Your Average Rock

Imagine it is a beautiful summer day. You have been lying around observing the clouds as they effortlessly float along. You decide to get up and explore your backyard for hidden treasure. As you are wandering through the freshly cut lawn, you notice a beautiful rock. While examining your rock, you vaguely remember a conversation your science teacher had about rocks and minerals. Could this be a mineral?

Minerals are substances found in nature. They are classified as inorganic solids. Minerals have a specific chemical composition, an orderly internal structure, and a characteristic set of physical properties. There are four basic questions that scientists ask to determine if substances are minerals. The first question focuses on the mineral as an inorganic substance. Humans, plants, animals, and single-celled organisms are classified as organic. Organic materials are living or were once living. Minerals are only made of non-living substances. The second question asks whether the mineral occurs naturally. To be a true mineral, it must be made in nature. Man-made substances cannot be minerals. The third question focuses on the structure of the mineral. Minerals are crystalline solids. They have a specific internal crystal structure. Non-minerals do not have this structure. The last question scientists ask is whether the substance has a consistent chemical composition. Minerals generally have a specific chemical formula. Though there may be small variations in the chemical structure, most molecules of the mineral look the same. Rocks are usually made from a variety of substances melted together. Different molecules from the same rock can look very different from each other.

There are different types of minerals that exist on our planet. In fact, scientists have found over 3,000 minerals. There are only twenty of these minerals that are common. Common minerals are called rock-forming minerals. Rock-forming minerals are part of the rocks that make up our planet's crust. Ten out of the twenty common minerals on our planet make up 90% of the mass of the Earth's crust. So what are these ten important minerals? They are calcite, biotite, dolomite, halite, gypsum, orthoclase, quartz, ferromagnesian minerals, plagioclase, and muscovite.