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Minerals are not made by people; they are … …naturally occurring substances. Minerals • • • • Natural Solid Inorganic Definite chemical composition • Crystal structure due to internal arrangement of atoms http://www.minerals.net/gemstone/index.htm Physical Properties of Minerals (can be used to identify the mineral) Color • Can be misleading • Can vary with the type of impurities Physical Properties of Minerals (can be used to identify the mineral) Luster • Surface reflection • metallic = shiny like metal • non-metallic = dull, non-shiny surface Pyrite has a metallic luster Calcite has a non-metallic luster Physical Properties of Minerals (can be used to identify the mineral) Hardness • How easily a mineral scratches materials • Mohs Hardness Scale • Scale from 1 (softest) to 10 (hardest) • Test by seeing if the mineral can scratch different objects (like human fingernail, copper, penny, glass, steel file) Sfaldatura (Cleavage) Tendenza a rompersi lungo piani paralleli alle facce dell’abito cristallino. Determinata dal reticolo Cleavage & Fracture – The way the mineral breaks – Cleavage—minerals break along smooth, flat surfaces and every fragment has the same general shape – Fracture—minerals that break at random with rough or jagged edges Streak • The color of the powdered form of the mineral • The color of the streak can be different than the mineral • Minerals must be softer than the streak plate Streak…can help identify quartz http://www.childrensmuseum.org/geomysteries/cube/b3.html Groups of Minerals • Minerals are grouped by the elements they are made of. Beryl (Emerald) Calcite Amethyst Mineral Group Characteristics Non-Silicates Silver •Make up only 5% of the Earth’s crust •Include some of the most important minerals Examples iron, copper, gold, silver, diamonds, rubies Copper Diamond Gold Ruby Iron Mineral Group Characteristics Carbonates Examples •Carbon & Calcite (CaCO3) oxygen and a positive ion, such as calcium Calcite with Duftite inclusions Mineral Group Characteristics Oxides Metallic ion and oxygen Examples Hematite (Fe2)O3 Mineral Group Characteristics Sulfides Sulfur and a metallic ion Examples Galena (PbS) Mineral Group Characteristics Sulfates Barite on Calcite BaSo4 / CaCO3 Metallic ion, Sulfur & oxygen Barite BaSo4 Examples Barite (BaSO4) Mineral Group Characteristics Native Elements Single elements Examples Gold (Au), Diamond (C), Silver (Ag) Mineral Group Characteristics Silicates Examples •Contain oxygen Quartz, mica & silica •The most abundant group of minerals MICA Quartz Special Characteristics the “Acid Test” Carbonates react with dilute HCl and other acids by fizzing or bubbling (releasing CO2 gas) Special Characteristics Fluorescence • Some minerals will glow when placed under short-wave or long-wave ultraviolet rays http://www.sterlinghill.org/Tour%20information.htm Special Characteristics Salty Taste • DO NOT TASTE MOST MINERALS! http://mineral.galleries.com/scripts/item.exe?LIST+Minerals+Halides+Halite Special Characteristics Magnetism • Many iron minerals will produce an invisible magnetic force field http://www.minerals.net/mineral/oxides/magnetit/magneti4.htm What do all minerals have in common? All: 1. 2. 3. 4. Are formed by natural processes. Are NOT alive and NEVER were alive Have a definite volume and shape Are elements or compounds with a unique chemical makeup 5. Are made up of particles that are arranged in a pattern that is repeated over and over (called a CRYSTAL) How do minerals form? • 1) Cooling of magma (hot, liquid rock and minerals inside the earth (from the mantle)) – Fast Cooling = No Crystals (mineraloids) – Medium Cooling = small crystals – Slow Cooling = large crystals How do minerals form? • 2) Elements dissolved in liquids (usually water) 1.What element are diamonds made from? 2. What do all crystals have in common? Cleavage or Fracture? 1. 4. 2. 3. 1. If a mineral can scratch your fingernail, the mineral is _______________ than your fingernail. 2. What is luster? Review