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Welcome to our Blog!

Posted by Roger Duncan on

Welcome to our blog!
 

Welcome to our first blog.  Check back with us from week to week to get great tips and information on Mining Metallurgy, Geology and more.

How to Interpret and Assay.

Recently at a the Denver Gold show this past weekend I got in conversation with a fellow mining engineer and colleague about interpreting assays.  I am always seeing ads in the mining magazines advertising Claims running  6oz or 10oz to the Ton etc.  Mostly I call BS on those types of numbers,  but many people get dupped into this and invest in an operation or buy a claim based on these numbers.  Now, many times the person that had the assay done got results back that did say 6oz or 10oz per ton.  What that person doesn't understand is how to properly interpret that assay.  So I will attempt to put that into laymen terms.  Let's say you sample a vein that say is 12 inches wide, and you take a sample and have it assayed and lets say it comes back at 5 ounces to the ton.  First impression is that is very good, and so simple math says if I had 100 tons I would have 500 ounces of gold.  This is flawed because you can't just mine a 12 inch vein and not take any of the other rock.  A typical small mine tunnel needs to be probably a minimum of 8 feet wide and 6 to 8 feet tall.  So for math purposes lets say it is 8 x 8 which is 64 square feet.  Lets assume the vein is 12" wide and runs from the top to the bottom of the face.  So that is 1ft x 8ft or 8 square feet.  So 8 divided by 64 is .125 or 12.5% of the total area.  So if the Assay ran 5 oz per ton but you have to dilute the assay by the same amount.  5 x .125 = .625 oz per ton.  So in order to mine this your average grade would come out to a little over 1/2 ounces to the ton.  Still a decent grade, but 100 tons of Ore will only yield 62.5 ounces of gold not 500.  That is also assuming a 100% recover rate which won't happen, but that is another topic for another day.

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