The problem I see with black sands is they are very high in Iron, magnetite and hematite, smelting, may just make a blob of Iron mixed with what little gold the had in them, that is if you were able to convert them to metals without them oxidizing in the melt making a slag of iron and tiny bits of gold locked up in them, Limestone (caco3), coal (coke), quartz (SiO2) are used to convert these iron oxides to metal in blast furnaces, not something easily done in your backyard.
just maybe with a flux very high in carbon (sodium carbonate) (or other carbon source like limestone) (coal and coke)to convert oxides of Iron and sand, borax to help make sand or quartz a glass slag for base metals to gather, something like fluorspar to help dissolve and make liquid, and a metal collector like lead, you may get a small bead, like they would in an assay, but by the time you wasted all of that time experimenting failing and wasting of furnace gas and dissolving good crucibles to find a mix that may yield tiny minimum amounts of gold, you would probably still find yourself in the hole as far as cost.
My thinking is if you can not classify it and pan it out is most likely not worth fooling with unless you had many tons of this, then sell it to china.
Sluicing, blue bowl or shaker tables if you have more than you care to pan.
Trouble with leaching is getting rid of all that iron; it wastes all your money on acids and oxidizers trying to get the iron out.
This is just my uneducated answer to your problem
