Minerals

What is a Mineral? Solid Naturally Occurring Inorganic Definite Crystal Structure Definite Chemical Formula

Minerals are Identified by their Physical and Chemical Properties Crystal Structure Color Luster Streak Breakage Reactions with Acid Other Special Properties Hardness Specific Gravity (Density)

Crystal Shape Cubic Monoclinic the crystal shape results from the atomic arrangement into geometric patterns when the mineral forms Cubic Monoclinic

Color Usually the first and most easily observed but the least accurate property -one mineral may come in many colors; the color is the result of minor impurities -bottle makers took advantage of this fact glass with gold Silicon from Michigan had iron in it so the bottles were green. When that source was depleted, Coke used other material and the bottles were white.

Changing Color in Glass and Minerals Compounds Colors iron oxides greens, browns manganese oxides deep amber, amethyst, decolorizer cobalt oxide deep blue gold chloride ruby red selenium compounds reds carbon oxides amber/brown manganese, cobalt, iron black antimony oxides white uranium oxides yellow green (glows!) sulfur compounds amber/brown copper compounds light blue, red tin compounds white lead with antimony yellow

Color -different minerals are the same color

Luster appearance of a mineral’s surface as it reflects light Metallic – look like shiny car Nonmetallic Glassy shine Muted shine Dull shine

Streak Color of the mineral’s powder as determined by rubbing the mineral on a piece of unglazed porcelain called a streak plate

Breakage Minerals break along lines of weakness in their crystal structure Cleavage occurs when a mineral splits or cracks along flat planes Fracture occurs when a mineral breaks at random lines

Reactions with Acid Minerals in the Carbonate Family (-CO3) react chemically with acid to produce carbon dioxide gas Reaction creates bubbles of gas and the mineral appears to fizz

Hardness Mohs Scale Mineral hardness was in use as long ago as 300 BC Current system was invented by German scientist in 1812 Based on a mineral’s resistance to being scratched

Minerals in Mohs Scale softest hardest

Hardness In the field, common objects are used to determine hardness. >2 fingernail 3 penny ~5 steel of a pocket knife 5.5 glass 6.6 steel of a file 7 quartz crystal 8.5 emery

Modern Versions of the Brinell Hardness Tester A hardness test for metals was developed by Swiss engineer Johan August Brinell in 1900. He evaluated strength by using a tiny cannon to shoot small steel balls into a sample and mathematically analyzing the results. Modern Versions of the Brinell Hardness Tester

Sapphire is related to Corundum, #9 on Mohs Scale Apple was trying to develop sapphire screens for iPhones.

Special Properties Magnetism Taste Smell Fluorescence Phosphorescence Refraction Electrical Radioactive

Specific Gravity Similar to density, which is the amount of matter in a given space (Mass/Volume) Compares density of the sample with the density of water Determined by dividing the mass of the sample by an equal volume of water <3 is nonmetal, >5 is metallic Tells you how many times more dense than water the mineral is