ENV100Y5 Lecture Notes - Lecture 33: Surface Mining, In Situ Leach, Mountaintop Removal Mining

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13 Feb 2016
Lecture 34 – Mineral Resources and Mining II
-Salt is mined and it occurs in deposits under the ground and it dissolves
-Solution mining (in-situ recovery) is when resources in a deep deposit are dissolved in a liquid
and siphoned out
-Some other things that are done with solution mining are lithium, boron, bromine, potash,
copper, uranium
-Solution mining can also be problematic, as it could get in contact with groundwater or other
problems. One solution for these problems is “subsidence”
Strip Mining
-Stip mining is when you strip off the surface layer of overburden and it’s often used for coal (i.e:
gravel, used in Alberta)
It can lead to acid mine drainage
Acid mine draining is a big problem associated with strip mining
Putting sulphur in contact with air and water, you get sulphuric acid. Coal contains
LeadOr and ZincOr are sulphite minerals where the acid runs off and this is toxic for the
Acid mine drainage can happen in any type of mine and can continue to happen even
after the mine has been closed
As the sulphuric acid runs off, it leaches metals from the rocks, many of which are toxic
and this toxic liquid is called “leachate”
This occurs when there’s effluent; this is the contaminated liquid runoff
Mountaintop removal reshapes ridges and valleys and it’s an extension of strip mining
The entire mountaintops are blasted off and the rock waste is dumped into valleys
The mountain top material is dumped in the adjacent valleys and this isn’t good the rivers
in the valleys or the people that live in those valleys
Open-Pit Mining
-It’s used for evenly distributed minerals
-It’s used for the big holes in the ground
-You don’t have to go deep underground
-There’s terraces in the hole so that workers can move down
-It’s used for copper, iron, gold, diamonds, coal, where they’re more close to the surface
i.e: quarries are open pits for clay, gravel, sand, stone (limestone, granite, marble, slate)
If you’re mining diamonds, would you have a high or low proportion of gangue to or?
The answer is high, and that’s because you’d have tons of waste rock
Placer Mining
-It uses water and gravity to isolate heavy materials
-When you go to the beach and you dig a hole in the sand, there’s a black layer in the sand. That
black thing is a heavy mineral that’s controlled by the waves
-Emeralds and other gems are often mined by this type of mining
-Placer mining uses running water, miners sift through material in riverbeds
-There’s also some mining that occurs in the ocean
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