Sign in to follow this  
Followers 0
Guest flintgreasewood

Bioleaching Of Black Shales

19 posts in this topic

Does anyone have extensive knowledge of bioleaching of black shales that they would be willing to share?

Share this post


Link to post
Share on other sites

We started talking about this on another forum. In general, bioleaching is a method of dealing with acid forming sulfides in ores. It is not a gold recovery method, its a method to pre-treat the ores prior to cyanide because acids formed from sulfides destroy cyanide (and once the cyanide is destroyed, it cant be used to recover the gold and silver. A number of mines in Nevada use strains of bacteria to oxidize sulfides like pyrite to form acids that can be neutralized - the process is called bioleaching. The neutralized ores, now free of their acid generating sulfides are treated by standard cyanide methods. It is an alternative to treating sulfides in an autoclave.

 

Here is a link to an interesting scientific paper on recovering base metals like copper using bioleaching:

http://hal.archives-ouvertes.fr/docs/00/51/28/15/PDF/Spolaore_Hydromet.pdf

Share this post


Link to post
Share on other sites

Economic viability rules the gold recovery game for sure. Shale and cyanide go together real well usually but much testing needed first. No ez answers to hardrock mining.John

Share this post


Link to post
Share on other sites

Most of the Carlin trend ore is limy shales and shaley limestones, and as Carlin is the most productive gold district in the US, its hard to say that shales are not productive!

Share this post


Link to post
Share on other sites

Chuck,

    The black shale is here in Colorado.  No one around here is doing anything with shales except the oil companies.  In fact I can't find any faculty at Colorado School of Mines or CU who have a clue about bioleaching except for one who is on sabatical in Oz. and he doesn't answer his email.

Share this post


Link to post
Share on other sites

Chuck

   Thanks for that input.  So far what I have determined from my research into the subject is that the "common" way to bioleach using concentrated bacteria native to the particular shale is to crush the shale to 1/2 inch minus [i believe] and spray long piles of the crushed shale allowing the liquid to percolate.  The leachate is collected and resprayed many times for as long as a year and a half.  When it is determined most of the metals have been leached out, the leachate is subjected to precipitating chemicals and the metals recovered.

   Currently, I have samples of my shale undergoing a bioleach [though admittedly, very unscientific].  I have finely crushed [100 mesh] and coarse crushed [1/2 inch minus] to which I add from time to time concentrated sulfur compounds.  I also keep the ph low with sulfuric acid.  After I return from Alaska in the fall, I'll pull off the leachate and do a precipitation...see if I get anything.  The electron microprobe analysis of the shale does not indicate gold but it my be in a micron size too small for the probe to pick up.  the probe does show copper, zinc and stibnite. as good players.

Share this post


Link to post
Share on other sites

No, it's not thiosulfate bioleaching.  Bacteria cultures are often taken from groundwater that has percolated through the shale to be mined.  Added to that are similar acidithiobacilli, eg, acidithiobacilli ferrens, and the process proceeds as I outlined.  The only way the process is economical is to have literally billions of tons of the shale and time to let "nature" work on the piles being processed.  Piles are continually being rotated in and out of production so you eventually have a steady stream of metals.

   As for me, I'm just playing around with the stuff to see if I can get my rude process to work.  If it were ever to be viable, I have located plenty of shale that can be staked.  For now gold is what I'm yearning to mine :).

Share this post


Link to post
Share on other sites

Chuck,

   Thanks.  Just A.D.D. :)  Often I wish I would work smarter, but then hard work keeps one in good shape.  Since we're not up in Fairbanks working in the shaft, I'm shoveling snow to get ready...we've received about 3' in the past week...more on the way on Monday.  But we'll be on our way north the 1st of May...about damn time!

Share this post


Link to post
Share on other sites

Chuck,

    What's your first order of business when you get to your claims?  I wish you great success in the upcoming mining season.  We're driving up with a small trailer load of stuff for the mine.  Really looking forward to the trip and all the fun, hard work ahead to get that gold out of the ground!

Share this post


Link to post
Share on other sites

Thanks, Chuck.  I'll check it out.  There is a lot of "normal" in many places, but in other areas it is anything but.  There's a new Colorado gold rush going on in the outwash plains of the northern Front Range.  Lots of new gold deposited.  I'm heading up into the hills this week to some historically rich drainages with my detector, shovel and pan.  Got to pack it in on my mountain bike and then hoof it.  Should be really interesting.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0