Minerals

What are minerals? They are found in nature. They have a solid, crystalline structure. The calcium and phosphorous found in milk are not minerals because they are suspended in liquid and are not crystalline. They are inorganic.

Two Groups of Minerals

Silicate Minerals feldspar Minerals that contain both oxygen and silicon. Make up 90% of the Earth’s crust. Silicon and oxygen will combine with aluminum, iron, magnesium, and potassium. Most common are quartz, mica, and feldspar. feldspar

Nonsilicate Minerals silver fluorite galena Minerals that do not have the combination of oxygen and silicon in them. Made of elements such as carbon, oxygen, fluorine, and sulfur. Come in different classes such as native elements, carbonates, halides, oxides, sulfates, and sulfides. silver fluorite galena

Properties of minerals Luster Cleavage and Fracture Hardness Color Streak

Luster The way a surface reflects light. Metallic - shines like metal such as gold, silver, and galena. Non-metallic varies. Quartz is glassy and talc has a pearly surface. Others will be waxy, silky(fibrous), resinous(plastic), and earthy.

Cleavage and Fracture Cleavage is the splitting of a mineral into pieces that have flat surfaces. Fracture is where the mineral breaks unevenly along curved or irregular surfaces. Minerals vary in the number of directions they split and in the angles where the flat surfaces meet.

Cleavage and fracture Mica- splits in one direction and forms sheets. Halite cleaves in three directions and forms cubes. Diamonds will break in 4 directions forming pyramids. Quartz breaks into pieces and forms irregular shapes (fracture).

Hardness The hardness of minerals is done by scratching one mineral with the other. The harder mineral will scratch a softer mineral. The Mohs scale of hardness is how the hardness is determined.

Mohs Scale of Hardness 1.Talc 6. Orthoclase 2. Gypsum 7. Quartz 3. Calcite 8. Topaz 4. Fluorite 9. Corundum 5. Apatite 10. Diamond

Color The color of minerals depends on the color of the substances that make up the crystals or from chemical impurities. Pure quartz is clear but the impurities can make it appear pink, green, or black. Color is usually not a good way to determine what a mineral is because of how it can change as conditions change; exposure to oxygen for example.

Streak The color of a mineral in powdered form. It can be shown by rubbing the mineral against a piece of unglazed porcelain called a streak plate The streak is not always the same color as the mineral because it isn’t affected by air or water so it is more reliable for mineral id.

Special Properties Density or specific gravity -The ratio of the density of a mineral in comparison to water is called specific gravity. Fluorescence- ability to glow under UV light. Magnetic Chemical reactions Optical properties - Calcite will cause a double image Taste Radioactivity

Formation 8. A. Magma - crystals form from magma cooling as it rises to the earth’s surface. slowly - forms large crystals that are visible. quickly - forms small crystals that are not visible to the eye without help. B. Solution- minerals that have been dissolved in water (like salt water). As the water evaporates, crystals form.

Types of Crystalline Structure cubic http://www.curriehj.freeserve.co.uk/ tetragonal http://skywalker.cochise.edu/wellerr/crystals/tetragonal/6wulfenite-mimetite-cochise103f.jpg

Hexagonal Orthorhombic http://journals.iucr.org/d/issues/2002/06/01/an0614/an0614fig3.gif

monoclinic http://www.museums.udel.edu/mineral/mineral_site/education/CrystalClasses/monoclinic/monaxisbox.jpg http://www.thunderhealing.org/rock/eudidymite.jpg triclinic http://www.cobweb.net/~bug2/mag.JPG http://www.museums.udel.edu/mineral/mineral_site/education/CrystalClasses/triclinic/triaxisbox.jpg

Formation of Minerals Evaporating salt water - When a body of salt water evaporates (dries up) minerals such as halite and gypsum crystallize. Limestones - Surface water and ground water carry dissolved minerals into lakes and seas where they crystallize on the bottom. Calcite and dolomite are examples. Solutions! Dissolved Minerals in liquid. When a . . . . Dries up, gypsum and halite. Limestone . . . Ground water; materials. Calcite, dolomite.

Formation cont’d. Metamorphic Rocks - due to changes in temperature, pressure, or chemical makeup, rock is altered. Calcite, garnet, graphite, hematite, magnetite, mica, and talc are formed in metamorphic rock. Hot water solutions - As groundwater works its way downward, it is heated by magma and reacts with minerals to form a hot liquid solution. Dissolved metals and other elements crystallize out of the hot fluid to form new minerals. Gold, copper, sulfur, pyrite, and galena are examples.

Formation cont’d. Pegmatites - As magma rises up through the earth’s surface it can form teardrop-shaped bodies called pegmatites. The crystals become very large. Many gemstones such as topaz and tourmaline form in pegmatites. Plutons - As magma moves up through the crust, it stops moving before it reaches the surface and cools slowly forming millions of crystals. The whole body eventually cools forming a pluton. Mica, feldspar, magnetite, and quartz are examples.

A mineral deposit that is large enough and pure enough to be mined for profit is ore. Rocks and minerals are removed from the ground by one of two methods: surface mining or sub-surface mining. The method chosen depends on how deep the mineral ore is located.

Utah’s Kennecott Copper mine. The world’s largest open pit mine. http://utahrockclimbing.com/images/Kennecott_Copper/smKennecottPITwide.jpg Utah’s Kennecott Copper mine. The world’s largest open pit mine.