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Minerals What is a mineral? Mineral- a naturally occurring, inorganic, solid that has a specific crystal structure and chemical composition. 1)Naturally occurring & Inorganic- made by the earth of non-living material. Examples - quartz, sulfur, diamond, gold, silver Non-examples - brick, glass, steel (man-made) 2)Crystal Structure- the repeating pattern that the particles within a mineral form. 3)Solid- Molecules are tightly packed into a rigid structure. 4)Specific Chemical Composition- the elements that make the minerals have a definite chemical formula. Naturally occurring and inorganic -To be considered a mineral it must have been formed by natural geologic processes, and never been part of a living thing. Gypsum Calcite -Laboratory created gems (synthetic diamonds, rubies, etc.) don’t count. Mineral or not? -Sugar? -Coal? -Salt? Crystal Structure • Crystal – A solid in which the atoms are arranged in a repeating pattern. Why do you think minerals that look like these are more rare? Most times, crystals aren’t formed in a open space and are mixed with other substances. SOLID • Solids have a definite shape and volume, which gasses and liquids do not. Therefore, no gasses or liquids can be considered a mineral. MINERAL NOT NOT Specific Chemical Composition • There are about 4000 known minerals on Earth. Each one is a unique substance with its own chemical formula. A few are formed from a single element. Most minerals have are made of mixtures of elements. How are these minerals created? 1) From Magma – Magma is less dense than the surrounding solid rock, so it rises and cools in the upper layers of Earth’s interior where it hardens. -The type and number elements in the magma will determine which mineral is formed. 2) From Solution – Minerals are often dissolved in water (for example, sea salt). When the liquid becomes “overfilled” with the mineral, solid minerals will begin to form in the water. IDENTIFYING MINERALS • Luster – The way in which a mineral reflects light. • Hardness – A mineral’s ability to resist being scratched. • Break – The shape a mineral takes when breaking (based on crystal structure). • Streak – The powder left behind by a mineral when scratched. • Color • Density • Other – Mass/Volume properties – Unique properties that some minerals possess. LUSTER • • Non-Metallic – Any mineral lacking the metallic look is considered non-metallic. Metallic Luster – Not all minerals with metallic luster are metals. Minerals in this category can be divided into 3 subcategories: GLASSY LUSTER DULL LUSTER WAXY/WET LUSTER HARDNESS - The measure of how easily a mineral can be scratched. • A mineral’s hardness is the most reliable and useful test for identifying minerals. • Friedrich Mohs developed a scale by which an unknown mineral’s hardness can be compared to 10 minerals of known hardness. MOHS HARDNESS SCALE Mineral Name Hardness Hardness of common objects Diamond 10 Corundum 9 Topaz 8 Quartz 7 Streak Plate = 7 Feldspar 6 Steel Nail = 6.5 Apatite 5 Glass = 5.5 Fluorite 4 Calcite 3 Copper = 3.5 Gypsum 2 Fingernail = 2.5 Talc 1 How is a diamond shaped? A mineral that cannot be scratched by your fingernail but can be scratched by glass, has a hardness value of_______? 2.5-5.5 A mineral that scratches glass but gets scratched by the steel nail has a hardness value of 6 ______? BREAK – The shape a mineral takes when breaking. Cleavage – a mineral that splits easily and evenly along flat planes where atomic bonds are weak. (Having a pattern) Fracture – Minerals that break with rough or jagged edges because of tightly bonded atoms. (random/no pattern) STREAK HEMATITE Sometimes, the same mineral will look slightly different due to small chemical impurities, but the streak will look the same. Do you think that mineral color is always the same as the color of the mineral’s streak? Color While mineral color is one of the less reliable clues to a minerals identity, it’s a good starting off point. The presence of trace elements and compounds in the mineral will determine its color. Density- how heavy is the mineral? Some minerals are heavier than others, meaning they are more Galenaextremely dense. They have more molecules heavy mineral packed into a given volume, making them weigh more. Also used as the rare mineral “unobtainium” in the move Avatar. Other Properties Some minerals have other unique characteristics that determine their identity. Smell - Sulfur smells like rotten eggs Magnetism - Magnetite is magnetic Taste - Halite tastes salty Fluorescence- glows under UV lights Franklin County, NJ has the most Florescent mineral mined collection in the world!!!! The Economy of Minerals Ore – A rock or mineral that contains a valuable substance which can be mined for profit. Iron Ore BEFORE Gold Ore AFTER The Economy of Minerals Gem – Valuable minerals that are prized for their rarity and beauty. Diamond Topaz Ruby Emerald Sapphire MINERAL IDENTIFICATION PROCEDURE After completing all tests, use your packet to identify the specific mineral name. 1. LUSTER- Is the luster metallic, glassy, dull, or waxy/pearly/wet looking? 2. HARDNESS – What is the hardness? Finger nail, copper coin, glass, steel nail, streak plate. 3. BREAK – Does it display fracture (random pattern) or cleavage (specific pattern)? If cleavage, specifically what type? (thin sheets, squared, cubic) 4. STREAK – Use the streak plate to determine the color of the mineral’s powder 5. COLOR – Give the mineral a DETAILED COLOR DESCRIPTION. 6. OTHER PROPERTIES – Does the mineral have any unique characteristics (smell, taste, magnetic, fluorescent, density, etc)?