Minerals

What is a Mineral? A mineral is a naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition. In order to be classified as a mineral, it must have all of these five characteristics.  Naturally Occurring  Inorganic  Solid  Crystal Structure  Definite Chemical Composition

Naturally Occurring It must be formed in the natural world The mineral quartz forms naturally as molten materials cool and harden deep beneath Earth’s surface. The following are NOT minerals, because they are made by people  Plastic  Brick  Glass  Steel

Inorganic The mineral CANNOT be formed from materials that where once living. Coal is NOT a mineral, although it is formed naturally in the Earth’s crust. Coal comes from remains for plants that lived millions of years ago.

Solid A solid always have a definite volume and shape The particles in a solid are packed so tightly together, so they cannot move

Crystal Structure The particles of a mineral line up together in a pattern and repeat themselves over and over again. Has flat sides called faces. The faces meet at sharp edges and corners.

Definite Chemical Composition Minerals always contain certain elements and in definite proportions. Almost all minerals are compounds. Example: Quartz is made up of one atom of silicon for every two atoms of oxygen Almost all pure (not compound) elements are solid and are metals Example: Copper, Gold and Silver are made of pure elements

How to identify Minerals Geologists have identified approximately 3,800 minerals. Since there are so many minerals, geologists needed a way to tell them apart Each mineral has characteristic properties used to identify it. Some characteristics are visibly identifiable

How to identify Minerals Identifying Characteristics  Color  Streak  Luster  Density  Hardness  Crystal Systems  Cleavage  Special properties

Color Only some minerals have their own characteristic color The color alone however, often provides too little information to identify the mineral **All three minerals are gold in color but they are different minerals

Streak Determined by a streak test It is the color of the minerals powder Test performed by running the mineral across a piece of unglazed porcelain tile The color of the streak is often different from the color the mineral appears

Luster Is a test that determines a mineral based off how light is reflected from the minerals surface. Minerals with metals are often shiny Terms used to describe luster o Bright o Pearly o Earthy o Waxy o Glassy

Density Density is the mass given to space (or per volume) No matter the SIZE the density will always be the same Density= Mass Volume You test for density by feeling the weight of the mineral in your hand

Hardness The best way to test types of minerals MOHS hardness scale Mohs hardness scale ranks minerals 10 minerals from softest to hardest Determined by scratch test (a mineral can scratch any mineral softer than it)

Moh’s Hardness

Moh’s HardnessMoh’s Hardness

Crystal Systems Classified by structures into six groups Based on the number and angle of the crystal faces Example:  Halite Crystals – six square faces that meet at right angles forming a perfect cube

Cleavage and Fraction The way a mineral breaks apart If a mineral breaks apart easily it has a property called a cleavage This has to do with the way the atoms in the crystals are arranged Most minerals do not split apart easily Fracture describes how a mineral looks when it break apart irregularly

Cleavage break

Fracture Break

Special Properties These occur only in some minerals  Magnetism  Glow under ultraviolent light (fluorescence)  Bends light  Reacts to acids