## Gold Mining on The Moon

The idea that it might be profitable to mine gold on the Moon (price of gold as of this writing is an astonishing \$44,868.30 USD/kg!) is motivated by the recent LCROSS results that detected 1.6% by mass of gold in the ejected plume. Since this keeps popping up in other threads, I figured I'd start a new one to collect the discussion in one place.

Originally Posted by RGClark
Originally Posted by Warren Platts
You should work backwards: 40 tons of gold per year at today's prices would bring in about \$4B/year. LCROSS said the gold was an incredible 1% of what was observed, IIRC. Taking that at face value, then 4 000 tons of regolith would have to be processed. (this agrees with what the participants said the value of the ore was.) All the equipment necessary could probably be brought in for 5 to 10 20-ton loads (a typical semitruck-trailer load is about 20 tons). If you could keep keep the overhead of the mine down to \$2B/year, you could make some money, potentially.
That seems high to me. For instance, 4,000 tons of regolith a year is a little more than 10 tons per day. It would seem to be high mass of equipment at 100 to 200 tons to process 10 tons per day.

I found some portable plants able to do gold processing using the Merrill-Crowe process after a web search:

Merrill-Crowe Zinc Precipitation Plants
For Recovery Of Gold & Silver From Cyanide Solutions
www.sepor.com/new/MerCrowe.pdf

This method precipitates the gold out after dissolving it in sodium cyanide solution. The two plant sizes available here have shipping weights of 1,200 lbs. and 3,100 lbs. and are able to process 65 tons/day and 300 tons/day of the solution, respectively. The amount of gold is given as usually no more than .10 oz. per ton of solution. So for the 300 tons/day plant it would be perhaps 30 oz. per day for a usual Earth mine. So for the lunar concentrations at perhaps 3,000 to 6,000 times higher than usual Earth mines, it might be 100,000 oz. to 200,000 oz. per day. However, it might not be this high because it might be limited by how much gold can dissolve into the solution at a time.
Another method for separating out the gold is called the electrowinning method, for which there are also lightweight portable plants available:

EW Pilot Plants.
http://www.sxkinetics.com/ewplants.htm

Bob Clark
This is interesting Bob. I didn't realize that a cyanide leaching facility could be so lightweight. On the other hand, the figure I provided above (around 100 to 200 tons total) also includes the other stuff you'll need, like a couple of hab modules, a whole suite of earth moving equipment, rock crushers and conveyers, and massive amounts of solar panels. Keep working on it.