Mining & Mineral Resources

1. Mining & Mineral Resources Chapter 16, Section 2: Mineral Exploration & Mining Standards: SEV4a, b, e

2. What are the steps in harvesting minerals? • Prospecting- finding places where ores occur • Mine exploration & development- learn whether ore can be extracted economically • Mining- extract ore from ground • Extraction- separate ore minerals from other mined rock • Smelting & refining- extract pure mineral from ore mineral (get the good stuff out of waste rock) • Transportation- carry mineral to market • Marketing & sales- find buyers & sell the mineral

3. How do we know where mineral deposits are located? • Airplanes can carry instruments that detect • Patterns of gravity • Magnetism • Radioactivity • Data is collected, satellite images are taken, and a geologic map is created. • Rock samples are taken & analyzed for their content & grade • Test holes are drilled to create a 3D estimate of the extent of the ore • This will tell the driller if the amount and grade of ore is high enough to warrant the cost of opening a mine. How Much Does a Mine Cost? Images of the Saline Valley in California. Left picture- red indicates trees, white indicates snow Middle picture- short wavelengths used to identify types of rocks Right picture- thermal infrared used to identify types of rocks that contain valuable minerals. Red indicates quartz

4. 3 Types of Mining • Subsurface mining • Surface mining • Placer mining

5. A. What is subsurface mining? • Mining of ore deposits 50m or more below Earth’s surface. (This is as long as an Olympic size pool) • 3 types of subsurface mining: • Room & Pillar mining • Longwall mining • Solution mining

6. 1. Room & Pillar Mining • Coal & Salt can be mined this way • “Rooms” are cut into a coal seam. Coal seam is a long, wide, layer of coal. • The “walls” of the room act as pillars to prevent collapse. • After all rooms of coal removed, the pillars are taken down starting with farthest away.

7. 2. Longwall mining • A shearer machine moves back and forth along the coal seam. • Sheared coal drops onto a conveyor belt and exits the mine • Hydraulic roof supports are used to prevent collapse

8. 3. Solution Mining • Potash, salt, sulfur are soluble in water • Hot water is injected into ore • Ore is dissolved • Removal of ore from water: • Compressed air pumped into dissolved ore and ore trapped in air bubbles that rise to surface… or… • Water evaporates from dissolved ore leaving ore behind.

9. B. What is surface mining? • Used when ore deposits are located close to Earth’s surface • 3 types • Open Pit Mining • Quarrying • Solar Evaporation

10. 1. Open Pit Mining • Soil & rock (overburden) are removed from top of ore deposit • Use explosives or heavy machinery • AKA- mountain top removal • Loaders remove the exposed coal • Pit is then refilled with overburden & covered with soil. • Some types of ore are taken to heap leaching ponds where mineral is removed from the ore rock. • Gold miners used to use mercury to extract gold but proved very poisonous to animals & plants • Now gold is extracted from ore rock using cyanide. Cyanide is also very poisonous. Bottom picture: Open pit gold mine with heap leaching cyanide ponds down below.

11. Machine used in open pit mining Bucket Wheel Excavator- cost $184,400,000 Takes 5 people to operate it, moves 10 meters per minute, power lines have to be removed when moving it.

12. 2. Quarrying • Open pit mine that is used to harvest • Granite • Marble • Sand • Gravel • Crushed rock (aggregates) • Clay • Gypsum • Talc Granite quarry in Elberton, GA LaFarge Granite Quarry in Douglasville, GA

13. 3. Solar Evaporation • Place sea water into shallow ponds • Water evaporates and leaves crystallized salt behind • 30% of world’s salt produced this way • Used largely in developing countries Salt evaporation ponds in San Francisco Bay. The beautiful colors are a result of harmless bacteria and brine shrimp that live among the salt. The colors vary depending on the “age” of the pond.

14. C. What is placer mining? • Rock with minerals weathers & disintegrates • Minerals carried by water in streams • As streams bend, the water slows, minerals fall out of slower water and accumulate as placer deposits • Can also occur along coastline where waves keep minerals from moving out to sea. • Use dredging to remove minerals • Bucket system that scoops sediment with minerals from bottom of body of water. • Minerals are separated from sediment Scoop placer deposits in bucket, deposit on barge, barge takes to refinery for separation.

15. How is mineral removed from ore? • Smelting • Crushed ore heated to high temps. • Impurities are trapped by a material called flux & create slag that forms a layer on top of the melted metal which is easily removed (but toxic) • Purified molten metal falls to the bottom of the furnace and is harvested. • Heap Leaching • Using chemicals to dissolve mineral from ore • Ex: cyanide used to remove gold • Ex: sulfuric acid used to remove copper Copper can be extracted thru smelting (top) OR thru heap leaching (bottom).