Mining & Mineral Resources

Chapter 16, Section 2: Mineral Exploration & MiningStandards: SEV4a, b, eMining & Mineral ResourcesWhat are the steps in harvesting minerals?Prospecting- finding places where ores occurMine exploration & development- learn whether ore can be extracted economicallyMining- extract ore from groundExtraction- separate ore minerals from other mined rockSmelting & refining- extract pure mineral from ore mineral (get the good stuff out of waste rock)Transportation- carry mineral to marketMarketing & sales- find buyers & sell the mineral

How do we know where mineral deposits are located?Airplanes can carry instruments that detectPatterns of gravityMagnetismRadioactivityData is collected, satellite images are taken, and a geologic map is created.Rock samples are taken & analyzed for their content & gradeTest holes are drilled to create a 3D estimate of the extent of the oreThis 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 snowMiddle picture- short wavelengths used to identify types of rocksRight picture- thermal infrared used to identify types of rocks that contain valuable minerals. Red indicates quartz

3 Types of MiningSubsurface miningSurface miningPlacer mining

A. What is subsurface mining?Mining of ore deposits 50m or more below Earths surface. (This is as long as an Olympic size pool)3 types of subsurface mining:Room & Pillar miningLongwall miningSolution mining

1. Room & Pillar MiningCoal & Salt can be mined this wayRooms 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.

2. Longwall miningA shearer machine moves back and forth along the coal seam.Sheared coal drops onto a conveyor belt and exits the mineHydraulic roof supports are used to prevent collapse

Middle picture is the shearer scraping a coal seam.Bottom picture is the hydraulic roof support73. Solution MiningPotash, salt, sulfur are soluble in waterHot water is injected into oreOre is dissolvedRemoval of ore from water:Compressed air pumped into dissolved ore and ore trapped in air bubbles that rise to surface orWater evaporates from dissolved ore leaving ore behind.

B. What is surface mining?Used when ore deposits are located close to Earths surface3 typesOpen Pit MiningQuarryingSolar Evaporation

1. Open Pit MiningSoil & rock (overburden) are removed from top of ore depositUse explosives or heavy machineryAKA- mountain top removalLoaders remove the exposed coalPit 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 & plantsNow 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.

Cyanide is very poisonous but does not accumulate in ecosystems like mercury which is probably why it is used.10Machine used in open pit miningBucket Wheel Excavator- cost $184,400,000Takes 5 people to operate it, moves 10 meters per minute, power lines have to be removed when moving it.

This would make an awesome Transformer!112. QuarryingOpen pit mine that is used to harvestGraniteMarbleSandGravelCrushed rock (aggregates)ClayGypsumTalc

Granite quarry in Elberton, GA

LaFarge Granite Quarry in Douglasville, GA

Small picture is talc quarry in France. For making talcum powder.123. Solar EvaporationPlace sea water into shallow pondsWater evaporates and leaves crystallized salt behind30% of worlds salt produced this wayUsed 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.C. What is placer mining?Rock with minerals weathers & disintegratesMinerals carried by water in streamsAs streams bend, the water slows, minerals fall out of slower water and accumulate as placer depositsCan also occur along coastline where waves keep minerals from moving out to sea.Use dredging to remove mineralsBucket 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.How is mineral removed from ore?SmeltingCrushed 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 LeachingUsing chemicals to dissolve mineral from oreEx: cyanide used to remove goldEx: sulfuric acid used to remove copper

Copper can be extracted thru smelting (top) OR thru heap leaching (bottom).