Geology 101Lab 2Monday, September 8, 2014Minerals: The Building Blocks of RocksChapter 3Importance of Minerals- Minerals are the building blocks of the rocks that comprise the solid eartho They are the physical foundation of our planet AND our society!- Common metals, such as aluminum, copper, and iron as well as precious metals such as gold and silver occur in the earth as mineral ores- Other minerals that we commonly use include:o Talc-bath powders and cosmeticso Halite-salto Micas-cosmetic powdero Graphite-pencil leado Gypsum-drywallo Calcite –antacid- The mineral data base in lab manual lists more and common usesBy Definition a Mineral Is:- Is a naturally occurring- Is an inorganic- Is a solid- Has an ordered internal molecular structure (a three dimensional arrangement of atoms)- A characteristic chemical compositionIs It A Mineral?- Bricko No-Man Made- Coalo No-Made of organic matter- Diamondo Yes- Graniteo No-made of many minerals- Iceo Yes- Oilo No- liquid and organicPhysical Properties- The crystalline structure and unique chemical composition of minerals gives each of them a unique set of physical properties- Physical properties are often used to identify mineralso Color (often unreliable) Ex: quartz, smokey quartz, rose quartz, citrine, amethysto Streako Crystal Formo Lustero Hardnesso Cleavageo FractureStreak- Color of the mineral in powdered form- Does not vary- Graphite has a silver-gray streak- Another example: o Hematite-Redisho Magnetite-jet blackCrystal Form- External expression of the internal molecular geometryo Quartz has a hexagonal crystal formo Note: if crystals are broken, you may not be able to see the original crystal formLuster- Appearance of a mineral in reflected light- Two basic categorieso Metallic: looks like a metal May be shiny metallic (brassy, silvery, etc) May be dull metallic (may look rusty, unpolished metal)o Nonmetallic-Everything else Terms used to describe: silky, earthy, pearlyo Submetallic- Ex: metallic luster: o Pyrite-Fool’s Gold- Ex:Nonmetallic Lustero Talc- Pearly lusterHardness- The resistance to abrasion of scratching- All minerals are compared to the Mos Scale of Hardness- This is a relative scale, so a mineral is considered “harder than…or softer than…”- For ex:o If you can scratch a mineral with you nail, it is softer than 2.5Cleavage- Describes the tendency of a rock to break along preferred planes of weakness- These planes of weakness can be described as where the atomic bonding between atoms in the crystal structure is week, and it is at those points that the mineral breaksFracture- Is a mineral property where the atomic bonding between atoms in the crystalstructure is perfect with no weakness- Fracture is basically either conchoidal or non-conchoidal- All minerals exhibit fracture, but when very strong cleavage is present, it can be difficult to see- Cleavage and fracture are mineral properties that describe the way a mineral breaks, but not the same thingOther Properties- Specific Gravityo Density compared to water- Reaction to hydrochloric acid- Natural magnetism- Smell- Taste- Double refraction- Malleability, elasticity, etcMineral Classification- Silicate mineralso Are the most abundant mineral in the earth’s crust, making up about 92%o Same fundamental building block, the silicon-oxygen tetrahedrono Four oxygen ions surrounds a smaller silicon ion- Non-Silicate Mineralso Not as commono Provide lead, iron, aluminum, other metalso Salt for food, plaster, drywall,
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