The 193,000 metric tons of gold discovered so far in mineral deposits (Singer 1995) would serendipitously fit into exactly 4 Olympic sized swimming pools, by my calculation. Might make them a little difficult to swim in though.
Well, since I’m on a roll with calculations:
this source - http://www.usatoday.com/tech/columnist/aprilholladay/2005-03-25-wonderquest_x.htm - says that the proportion of gold in ocean water can vary from 5 to 50 grams of gold in one billion liters.
Thus, if we had a machine that could process one million liters per day, it would take one thousand days - less than 3 years, to get somewhere between 5 and 50 grams of gold.
It seems to me that a gram of gold has been in the $20-$30 american range lately. So you might earn as much as $1500 bucks for keeping the machine running one thousand days, or as little as $100
How much did you want to make? 
In the mid 1980s, I got to go to Australia for a much-too-short period of time. While I was there, some of my Aussie friends took me out to Hill End, which was the site of a massive gold rush back in the 1860s. We got to talking with one of the locals (the village constable) and he told us that the gold “gave out” because with the technology of the day, they couldn’t get to any more of it. It’s estimated that they only got about 15% of the gold from Hawkin’s Hill.
However, there was so much land fraud committed that no mining can occur using modern equipment and technique, because the claims were still tied up in court cases more than a century later. Apparently, some of this has been resolved, as I see that there is a new Hill End gold mining company doing business.
I think this is exactly what people want: if you can find money in the ground, then you could easily be very rich! Values of “easily” are only high with ignorance of mining, processing, and economics, of course, but then, look at the set that wants a return to the gold standard.
Well once you’ve discounted the pumping costs, the magnetically activated carbon filter, the cyanide to strip the gold, and the electrolysis to then recover the gold from this solution, hmm the net cost by my calculation would be… you’re bankrupt.
Modify an organism to bioaccumulate the gold by several orders of magnitude, then get back to me.
according to this How much gold is there in the world? | HowStuffWorks, all the Gold ever mined would be approx the size of a cube 82 feet on each side, about 1/3 the size of the Washington Monument.
If you’re going to wait that long, the oceans will dry up in around a billion years. Then you get out the regular strip-mining machinery and go to it in the salt deposits left behind in the ocean basins. Cheaper and saves time!
As far as the amount of gold in jewelry vs. other uses, think of it on a per-person basis. A typical person might own a computer or two, or a few other electronic devices, each of which has a minuscule trace of gold in their circuitry. And the vast, vast majority of people don’t have any of the scientific equipment that uses gold at all. But a pretty fair fraction of people at least have a gold wedding ring. So I wouldn’t be at all surprised to find that well over half of the gold in use in the world is in jewelry or other “ooh, pretty” applications.
A number of years ago, the Gold Institute, or some sort of trade group, took out a full page glossy ad that showed the Washington Monument, that said, “All the gold we have had and all the gold we will ever have, would not fill this object.” I think that pretty much takes in the mined gold as well as the dissolved gold in the oceans, according to some of the estimates we’re reading here. So they were not far off.
Well the Gold Institute clearly haven’t reckoned on my plans to strip mine the remains of a collapsed neutron binary star. Of course the massive amounts of the metal I’d have would make it relatively worthless. Still I can build a shiny house out of it. Lightening strikes might prove an issue though.
You might be a trifle optimistic here.
According to my calculations a billion liters processed would net you $16.42 per day. You’re gonna need to keep that day job.
That’s assuming $900 dollar gold.
There’s also plenty of places in the Western US particularly where there’s still enough gold in the creeks to attract recreational panners, but not quite enough for it to be commercially viable. I’ve known some folks who do that and some days they’ll get nothing, but other days they can make over $100. I suspect the average return is somewhere around that of the billion liter-per-day ocean gold machine.
Hey, if Scrooge McDuck could do it I could do it.
I just wanted to share that, about an hour after reading the above I was reading Terry Pratchett’s Men At Arms and came across this sentence:
“Colon fished in his pocket and took out three sequin-sized Ankh-Morpork dollars, which had about the gold content of seawater.”
Gold would make excellent bullets: it’s incredibly dense, and non-toxic to animals. Ditto for fishing weights. More seriously, it’s wonderfully maliable, ductile, and heat and electrically conductive - and it doesn’t oxidize. It would be everywhere in products if it were cheap. At one time someone made a solid gold frying pan for Julia Child to try out; worked very well, but extremely heavy.
I don’t think gold would make a particularly good bullet, considering its softness and low melting point. It would probably leave all sorts of debris behind in the barrel. But certain gold alloys could work.
In view of the fact that gold is harder than lead and melts at a much higher temperature (1947 degrees F, vs 621), I’d have to question this.
Nobody said it was going to be easy. Especially with such a crappy invention 
Try harder!
Back to the OP.
Gold doesn’t just lie in chunks or in obvious veins. It can exist in minuscule amounts in other ore. Large scale copper mining can yield enough gold to change the economics of the copper mining process.
So, at some level you can make the analogy to oil. There’s a lot of it out there (in shale for instance), it just becomes a matter of the how economical it is to recover it. Watch gold mining stocks over time. Some gold mining companies can’t make money when gold is $300/oz. Yet, at $1,000/oz. their stock looks pretty attractive.
Well a ‘ooh shiny’ Krugerrand that is about the size of a US 50 cent piece is worth about $1000 right now. Stay amused, but it’s not just pretty.