Gentlemen,
Here’s the link if anybody wants to D/L the USGS publication:
http://pubs.usgs.gov/circ/1969/0609/report.pdf
A few years back I looked at mercury vapor samplers. You can pick used ones up on eBay for a few hundred bucks, but they are big (for a backpack) and battery operated – essentially all the things I don’t want to carry on my back to almost impassable locations in the Superstitions. However, on page 1 of the USGS circular is a method for gathering samples directly from the soil. They essentially set up 2 foot high plastic tents on the ground, placed some gold at the top and let the convection air current draw the air from the ground over the gold - which mercury will stick to. Here's the quote:
APPARATUS AND TECHNIQUE FOR MEASURING MERCURY IN SOIL GAS
Pyramidal tents of transparent plastic were used to funnel soil gas through gold or silver foil to trap mercury. The tents (fig. 1) were constructed of four pieces of 1/8-inch-thick Plexiglas, which were 2 feet wide at the base and tapered to 2 inches wide at the top; vertical height of the tent was 22 inches. The tent was formed by joining the Plexiglas panels with masking tape. A basket made of 80-mesh stainless-steel wire cloth was placed over the opening in the top and was secured with tape (fig. 2). The tent was then placed on the ground and soil was banked around its base to exclude free movement of air into it from the outside.
Gold or silver flakes (about 1 gram) were spread evenly in the wire basket, and a canvas sample sack was taped loosely over the top to prevent the flakes from blowing away (fig. I). The flakes were 0.007 inch thick and about 1/16 inch square. Under the influence of the sun's rays, the air temperature inside the tent immediately began to rise, setting up convection currents that carried the air in the tent upward through the trap. The tent was left in position for 2 hours, during which time 175 cubic feet of air passed through the trap. In practice, about 10 tents were placed along a traverse within a period of 2 hours and were then collected in order……..
Page 3 is interesting:
CONCLUSIONS
Mercury in soil gas collected at the surface has delineated part of the known gold deposits at Cortez, Nev., through as much as 100 feet of gravel. Mineralized veins and faults are readily detectable by measurement of mercury in soil gas…..
-=~ End of quoted passages ~=–
Also in the pamphlet are charts of samples taken over known gold deposits, in most cases you would need to be almost directly over the gold vein – BUT the part about mercury vapors being detectable through 100 feet of overburden (gravels in this case) was highly intriguing.
This is a do-able method of mercury vapor sampling in the Superstitions. Given the terrain and accessibility of the Superstitions, I don’t think it’s practical for large areas -> but if you happen to be in a section of the hills where you believe the covered shaft is located then it’s something to think about, isn’t it?
Clay's prediction that some future technology would be used to discover the LDM may come true after all.....
Best,
Ashton
