Minerals (Geology)

There is a difference between rocks and minerals. In fact, many people often believe they are the same things, but minerals may look like rocks, but they are made up of elements. A mineral is a naturally-occurring solid substance made from a single element or a combination of elements. Mineral examples include diamond, halite, jade, and nearly 4,000 more. Elements are pure substances made from a single type of atom and are the building blocks for all matter in the world. Element examples include hydrogen, oxygen, gold, and over 100 more, which are found in the Periodic Table of Elements.

A rock is a mixture of one or more minerals. A rock could be made of a single mineral, but many rocks usually contain two or more minerals. Rocks are solids and form naturally, but that is where the similarities stop. Two samples of the same type of rock may have different kinds of minerals in them, but a mineral is always made up of the same materials or elements in nearly the same proportions.

For example, granite is a type of igneous rock, and if one is found in a backyard in California, another granite rock found in Maine a few thousand miles away will likely not be composed of the same minerals. However, a ruby (kind of mineral) found in Australia will have a similar make-up as a ruby found in India.

The study of minerals is called mineralogy. Minerals are usually solid, inorganic, have a crystal structure, and are formed naturally through a serious of geological processes. A mineral can be made up of a single chemical element, such as a diamond, but most are usually compounds, composed of two or more elements.

There are four main characteristics of minerals, which makes a rock a mineral and not a rock. First, they are inorganic (nonliving) solids with a volume, meaning they take up space, and a rough shape- some may be roundish, somewhat rectangular, etc. Next, they have a definite chemical makeup of one or more elements or chemicals. Third, minerals usually have a crystal structure, though there are some that do not, and finally, all are formed by geological processes.

Minerals may form in several ways. For example, a mineral called halite forms when water evaporates in the hot, shallow part of the ocean and the halite (table salt) is left behind. Minerals are made when magma, or liquid rock, cools and turns into a solid such as talc, that is used to make baby powder. It forms deep in the Earth as high pressure and temperature causes changes in solid rock.

In addition, there are physical and chemical properties of minerals. Physical properties include the type of crystal pattern; their hardness as measured on a ten-point scale from softest to hardest called Mohs scale; luster or how it appears in light; its color; fracture or how it breaks; streak which is its color when its ground to a powder or rubbed onto an unglazed plate; cleavage, which is how it splits; and specific gravity, its density compared with water.

The chemical properties of minerals include four common groups and how they are composed and formed. There are silicates, which is the most common group all containing oxygen and silicon joined together such as aluminum, magnesium, iron, quartz, and mica. Carbonates are the second most common group and contain carbon and oxygen together with calcite a common mineral found in seashells. The third group is oxides which include refined metals such as tin and copper consisting of an element joined with oxygen, and finally sulfates forming in areas of slow evaporation such as where hot waters are forced through rock as with geysers.

There are thousands of different minerals but some of the most common include feldspar which makes up over 50% of the Earth's crust; diamond, which is the hardest mineral on Earth; and quartz, the most abundant mineral found at the Earth's surface. Three other well-known minerals include talc or sometimes known as baby powder; pyrite, which is often called 'fool's gold'; and of course, copper, one of the earliest metals used by ancient peoples.

In summary, minerals are used for everyday purposes from the graphite used to make pencils, the salt in foods, to the many mineral ores which are the source of metals.