Minerals A natural, usually inorganic solid that has a characteristic chemical composition, an orderly internal structure, and a characteristic set of physical properties.

Minerals are either elements or compounds. Earth’s crust has 90 naturally occurring elements. – Eight make up roughly 98% of the mass of the crust. – Most abundant elements of Earth’s crust: Oxygen = 46%* Magnesium = 4% Silicon = 28%* Sodium = 3% Aluminum = 8%* Calcium = 2% Iron = 6%* Potassium = 2% Minerals are not formed by life processes; they can form from magma and be deposited from solutions and gases.

Mineral? requirements Inorganic (contains no carbon from living things) – Not made up of living things or the remains of living things. Formed in nature (not man-made). Crystalline - Composed of crystals Solid Chemical composition is unique – Fixed chemical formula

Approximately 20 common minerals – 10 make up 90% of the mass of the earth’s crust – quartz, orthoclase feldspar, plagioclase feldspar, muscovite, biotite, calcite, dolomite, halite, gypsum.

Minerals make up rocks * igneous * metamorphic * sedimentary

Crystalline structure All minerals in earth’s crust have a crystalline structure. Crystals are solids with definite shapes and smooth flat surfaces called “faces”. Crystals are sometimes difficult to see; must use microscope or x-rays. Crystal shape can be used to identify minerals.

Crystal growth is determined by 1. time  rate of cooling – If slow, large crystals form – If fast, small crystals form – If very fast, no crystals form 2. space  how much room there is to grow – Little room, crystals grow smashed together – Lots of room, individual crystals can grow 3. impurities (other materials stuck inside)

Six basic crystal shapes

7 common mineral groups SILICATES – “SiO”(Silicon and Oxygen) 1/3 of all minerals (1000); most abundant group 96% of Earth’s crust; 50% quartz and feldspar Non-silicates CARBONATES – “CO 3 ”………70 different minerals OXIDES – “O” …………………150 different minerals HALIDES – must contain one  F, Cl, Br, I, At SULPHATES – “SO 4 ” SULPHIDES – “S” and a metal PHOSPHATES – “PO 4 ” Native elements – in their elemental form

Identifying Minerals Color Luster Reaction to light Hardness Cleavage or fracture Streak Form – crystal or massive Specific gravity (think of it as density) Special properties

Identifying minerals Color – Unreliable for most – Always need fresh break Streak – Color in powdered form, – Use streak plate Density – Does or does not have heft? – Is it heavy for its size?

Luster Reaction to light Transparent Translucent Opaque How light is reflected from a mineral’s surface – Metallic – Nonmetallic (waxy, dull/earthy, glassy, pearly).

Cleavage Fracture The tendency to break along specific planes of weakness. Form smooth flat surfaces = faces (due to weak bonds) Does not break along cleavage planes = fracture Irregular Conchoidal Fibrous Asbestos

Form Crystals Massive (no crystal shape is visible)

Hardness A measure of a mineral’s ability to resist scratching.

Special Properties – FLUORESCENCE AND PHOSPHORESCENCE Ability to glow under ultraviolet light Ability to continue to glow – CHATOYANCY AND ASTERISM Cat’s eye Star ruby – DOUBLE REFRACTION Ability to bend or refract light Double vision – MAGNETISM.. Yes or no – EFFERVESCENCE reaction to acid (bubbles) – RADIOACTIVITY Unstable atoms Geiger counter – Example: Uranium

Gems Rare or highly prized minerals. Physical properties that make them valuable are color, luster, hardness, and how light passes through them. Gem forms of minerals may be different than the mineral in its natural form – Due to impurities, crystal shape, color, or how it is cut or polished.

Examples of Gems