Minerals Properties of Minerals

What is a Mineral? A mineral is a naturally occurring, inorganic solid that has a crystal structure and definite chemical composition. Minerals must have the following 5 characteristics. – Naturally Occurring – Inorganic – Solid – Crystal Structure – Definite Chemical Composition

Naturally Occurring The mineral must be formed by processes in the natural world. Quartz forms from cooled molten lava and therefore is a naturally occurring mineral. Brick and glass are made in factories and therefore are not naturally occurring.

Inorganic Minerals cannot be formed from materials that were once part of a living thing. Coal is an example of an organic substance. It comes from fossilized plant and animal remains.

Solid Minerals are always solid, with a definite volume and shape. The particles that make up solids are packed tightly together, so they cannot move like the particles that make up liquid.

Crystal Structure The particles of a mineral line up in a pattern that repeats over and over again. The repeating pattern of a mineral’s particles forms a solid called a crystal. A crystal has flat sides, called faces, that meet at sharp edges and corners.

Definite Chemical Composition Minerals are made up of certain types of elements and these elements are in definite proportions. Almost all minerals are compounds, meaning they are made of 2 or more elements. There are a few minerals that are made purely from 1 elements. – Ex. Gold, Copper, and Silver=>

Identifying Minerals Geologists have discovered about 3,800 minerals. Each mineral has characteristic properties that can be used to identify it. Some examples of characteristics are color, streak, luster, density, hardness, crystal systems, and cleavage and fracture.

Color Geologists use color to filter down the amount of possible minerals it could be. Only a few minerals can be determined based purely on color. Azurite= blue Malachite= green

Streak A streak is the color of the powder that is produced by rubbing a mineral against a piece of unglazed porcelain tile. Ex. Pyrite has a gold color, but its streak is greenish black.

Luster Luster is the term used to describe how light is reflected from a mineral’s surface. Some of the terms used to describe luster are: Metallic luster, earthy, waxy, and pearly.

Density Density is the amount of mass in a given space. Two objects are the same size. One is heavier than the other. That is because the heavier one is denser. Density= Mass/Volume D=20g/20ml D=1g/ml

Hardness Friedrich Mohs created a scale to determine hardness of rocks. Mohs hardness scale consists of 10 minerals from softest to hardest. You scratch the unknown mineral with the known minerals to determine where it falls in the scale.

Crystal Systems The way minerals grow can differ. Some minerals grow into one of 7 crystal systems. The groups differ by the number of faces and angles.

Cleavage and Fracture A mineral that splits easily along flat surfaces has the property called cleavage. A mineral that breaks apart in an irregular way has the property called fracture. The arrangement of the atoms cause minerals to break apart in certain ways. The way it cracks can help determine the mineral.

Special Properties Magnetism: some minerals are magnetic. Fluorescence: some minerals glow under UV light. Radioactivity: some minerals give off radiation.