Cooper, B.L. (1994) Reservoir estimates for the Sulpicius Gallus region. Space 94: Engineering, Construction and Operations in Space, pp. 889-896. American Society of Civil Engineers, New York.
"Abstract: The Sulpicius Gallus area... of Mare Serenitatis, covering an area of approximately 6000 km2. It appears to contain an orange glass component that would be an excellent feedstock for hydrogen reduction. Because the glass occurs as a relatively pure material, and because it does not clump up very much, it would be easy to excavate. The deposits may be up to 50 meters thick in some places. Certain sub-areas may have thicker deposits than others (up to 50 meters), and spectroscopic evidence suggests that two areas in particular, which have the highest Mg/Al ratios, contain up to 66% pyroclastic glass on the surface. Estimates presented here show that 1.1x109 metric tons of oxygen could be produced from one of the enriched areas that have been detected by spectrographic studies.
Furthermore, the orange glass is known to have volatile-rich coatings, which could be extracted by gentle pre-heating of the material before the hydrogen reduction process begins. Thus, in addition to the oxygen, we could extract 8.8x106 tons sulfur, 5.8x106 tons zinc, 1.9x106 tons chlorine, 1.9x106 tons iron, 1.5x106 tons nickel, 5.1x105 tons copper, and 3.1x105 tons gallium, along with smaller amounts of many other elements. The upper 50 cm of the soil would also contain some solar-wind implanted volatiles, such as hydrogen, nitrogen, carbon, helium, and helium-3..."

Cooper also says in the article quoted above that the glass is located in two 300 km^2 areas, the best one being 40 km SSE of the crater Sulpicious Gallus because it is less mountainous.  This area might contain 9.77 cubic km. of glass or 19.5 billion tons.

Say we just excavate one 1/1000th of that or 19.5 million tons, that's in the range of regolith mining shemes proposed for mining volatiles, iron fines, etc. We'd get 1.1 million tons of oxygen; 8,800 tons of sulfur; 5,800 tons of zinc; 1,900 tons of chlorine; 1,900 tons of iron; 1,500 tons of nickel, 510 tons of copper, 310 tons of gallium.  That's not bad, and the glass beads just have to be heated to vaporize or melt these elements off their surfaces, though iron would be obtained by hydrogen reduction and nickel by carbonyl processing.  Extracting copper and zinc, used to alloy Al and Mg respectively, from regolith will be difficult.  Chlorine extraction from regolith is difficult too and would either be done by high temp pryolysis of apaptite in KREEP or H2SO4 leaching.  Simply heating volcanic glass is more appealing.

510 tons of copper would make plenty of electrical wires.  8,800 tons of sulfur would make plenty of sulfuric acid, about 27,000 tons of it.  1,900 tons of chlorine would make plenty of CaCl2 for FFC cell electrolyte.  310 tons of gallium would make plenty of GaAs thin film solar panels if we had the arsenic. 

See:
http://astrogeology.usgs.gov/Projects/LunarPyroclasticVolcanism/lunpyroWebDb.html
Volcanic Glass
David Dietzler, 2007
Volcanic glass, also called pyroclastic glass, is found in many places on the Moon.  The largest deposit is in the Ocean of Storms just west of the Aristarchus Plateau (area 37,400 km^2)  Besides mining the orange and green glass and melting and working it into different forms, it can supply many other elements.  It can be reduced with hydrogen to produce oxygen.  And we can melt it down and make green and orange glass items to go along with our cobalt tinted glass made from other feedstocks like silica from acid leaching or boiling anorthite at 1500 C. It could be mixed with Al2O3, MgO, Na2O and CaO to lower its m.p. and make it more workable.
Chlorine can be used to make CaCl2 electrolyte for FFC cells. It can also be used to make silane and SiCl4 that can be thermally decomposed to get rather pure silicon suitable for zone refinning to 99.999% purity and doping for semiconductor devices like big high voltage solid state rectifiers and invertors as well as solar panels.  Chlorine can also be used to make AlCl3 by carbochlorinating Al2O3 obtained by acid leaching of anorthite or calcium aluminate and AlCl3 can be reduced by electrolysis without flux or electrode burn up. AlCl3 can also be reduced to aluminum metal by manganese at 250 C. (Toth process). Sulfur can make sulfuric acid for leaching anorthite in aluminum extraction processes and it is a component of sodium-sulfur batteries. Also, H2SO4 leaching will produce plaster, CaSO4, for casting aluminum, magnesium and other uses like wall board by layering between two sheets of glass fiber cloth and medical/dental casts.  Copper can be used for aluminum alloys and zinc for magnesium alloys.  Gallium can be purified and doped with upported arsenic to make 30% efficient solar panels that might be mounted on vehicle roofs and used to power radio navigation tower transponders. 
NASA