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Heading: 1.1.1pyrite
Is there a technique by which aggregate producers could separate and remove iron pyrites from a natural aggregate contaminated with it?


Yes and no.

It all depends upon the character of the aggregate and Iron. For example, in massive limestone, it is likely the pyrite is disseminated throughout the rock mass making seperation uneconomic. On the other hand, if it is associated with shale seams in a laminated shale and limestone deposit, its possible that you may be able to "concentrate" the pyrite in the fines fractions. This assumes the shale is friable.

If the pyrites are not uniformly spread through your rock, perhaps selective mining may offer some hope by identifying and avoiding "hotspots".

Hope that helps.

Brian Glackin

I agree with Brian - reminding myself I am not a geologist. I recall pyrite removal in the processing of bottom ash cinders out of a coal-fired power plant. This was an Eastman Kodak plant in Tennessee, and thus a source of additional info on the subject. The "cinders" were used in concrete block manufacture, and if pyrites in "fresh" cinders were used, at some point in the future, 12-24 months, the pyrites manifested themselves in the face of the block exposed to weather by exhibiting a rust stain. To counter this, the cinder source "weathered" the cinders for 12-24 months before shipping to a block plant.
I recall the processing including the use of a magnetic separator on the conveyor belt pulley and that was somewhat effective.
As Brian says, you still have a potential where the pyrite particles are not exposed by the crushing.
Hope this has given you some food for thought.
Roy Keck
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