Minerals 8th grade

Mineral Groups 2 Major Groups 1. Silicate minerals – minerals that contain a combination of silicon and oxygen a)Feldspar minerals – most common in Earth’s crust Main part of all rocks on the Earth’s surface contain silicate minerals (ex. granite) b) Quartz – 6 sided crystalline form; most common mineral in sand c) Mica – soft and shiny; thin sheets d) talc – softest known

2. Nonsilicate Minerals – do not contain a combination of silicon and oxygen; usually classified by a chemical composition a) Native Elements – minerals with only one element b) Carbonates – contain combinations of carbon and oxygen (ex. limestone, cement, building stones) c) Halides – inorganic materials containing combinations of fluorine, chlorine, iodine or bromine with sodium, potassium, or calcium (ex. halite, fertilizers, and photographic film) d) Oxides – compounds that contain oxygen and 1 other element (ex. iron, aluminum) e) Sulfates – contains sulfer and oxygen (ex. gypsum and plaster of paris) f) Sulfides – contain sulfer and 1 or more metals (ex. pyrite)

Mineral Properties Many minerals can be identified by physical properties. Identifying minerals requires using at least 2 of the following properties: Color Luster – way surface reflects light Metallic – shiny luster Nonmetallic – not shiny, no reflection Hardness – resistance to being scratched that depends on strength of bonds between ions or atoms of a mineral Strongest mineral = diamond Scale of hardness = Mohs – mineral rubbed against surface of each on scale

Mineral Properties Streak – color of the powder left by a mineral when it is rubbed against a hard, rough surface (hardness of @ 7); better to identify than color Cleavage – tendency to split along set of parallel, flat surfaces Fracture – tendency to break along irregular surfaces Density – mass in grams/volume in cm3

Special Mineral Properties Taste – unsafe to use this property because many minerals are toxic Smell – strongest when just dug out of the Earth or struck Reactions to hydrochloric acid – to see if made of calcite Flexibility – able to bend thin layers with out breaking (ex. biotite and chlorites) Magnetic – ex. magnetite Lodestone= piece of magnetite that acts like a magnet

Special Mineral Properties Fluorescence – glow and change color under ultraviolet light Phosphorescence – continue to glow after ultraviolet light is no longer on them Refraction – bending of light waves due to change in wave’s speed as it passes through 2 substances Double refraction – ability of a mineral to produce 2 images Feel – jagged; smooth; greasy or oily Radioactive – ability to give off nuclear radiation as a result of a change in the atom’s nucleus (ex. uranium, radium, zircon)

Uses and importance of minerals Metals – good conductors of heat and electricity useful in electric wires make pots and pans for cooking high melting points malleability – ability to be shaped or formed by hammering or pressure (ex. aluminum, gold, silver, copper) ductility – ability to be drawn or pulled into wire (ex. copper or gold)

Uses and importance of minerals Native metals – metals not combined with other elements Ore – naturally, occurring rock from which a useful metal or mineral is recovered. Contain metal ions combined with other elements such as oxygen or sulfur Extracting methods – separation with magnets, electricity or heating to high temperatures in the presence of carbon or carbon monoxide

Uses and importance of minerals Alloys – minerals made of 2 or more metals or of a metal and a nonmetal; most important industrial material 1st to be discovered – bronze (alloy of copper and tin) resist corrosion have low melting points