Even if a camera that sees and differentiates gold only worked above ground, I can see a slight possibility of benefit : I used to drive a vacuum truck sweeper doing shopping centers , night after night, year after year, when I was younger. And when 500 cars move out of a shopping mall or Kmart parking lot each day, then you'd be surprised at the stuff lying around . Of course, it's mostly all trash, cig. butts, leaves, etc.... But occasionally valuables that perhaps rolled under a car. Or bills blown up against the cyclone fences at the far ends of the lot, etc....
And since md'ing is my hobby, I'd developed an eagle eye to spot $$ (bills, coins) on the lot. And several times, I even found gold jewelry at night. It used to rile my fellow workers, when ... each month, I'd come in with yet another gold ring or bracelet or something. They would start to furiously keep their eyes open for any keeper jewelry like that, but .... never found any, haha.
Thus a camera, that could do an entire 15 to 30 acre parking lot, and *only* signal off of gold, *could* be a benefit in a case like that. Even though we'd be talking about objects above the ground. Because I could never actually spot something, unless I was walking or driving right past it.
And I heard of a fellow in Hawaii, in the honeymoon high-rise hotel districts (people world-wide go there to honeymoon, as you know), had made sport of the following tactic : He claimed that he would go to the parking lots of the honey-mooner area hotels. And ... when the sun was rising or setting *just right* (ie.: just the right angle on the horizon), that he could visually scan entire parking lots, and find loose diamonds. Because they glinted/reflected in a way that broken glass chips did not.
And go figure: The peak time that a stone might fall out of a ring, is when it's brand new (not properly set during manufacture, faulty crown that was holding it in, etc...). And since Hawaii is filled with people wearing their rings for the first time, then ... odds are.... there would be some loose diamonds to be found. And supposedly his system worked. Or ... so he claimed.
That too would be another example of where "above the ground" might still have an application, in the case of the current discussion. But when/if it comes to anything other than paved parking lots, I can not see a use for this UNLESS it worked on buried objects too. And for that to be true, it would have to emit some sort of gas or vapor that comes through to the surface.
This is a popular folklore in some 3rd world countries. Who are convinced that there are fumes that gold gives off. Such that, for example, they will claim that there are little blue flames or glows that emit from a hillside, if gold were buried in the distant. Or that if you opened a treasure chest, you would immediately die if you breathed the vapors, etc... I hope we can both agree this is un-informed superstition. Thus, so too, am I doubtful that there is any "fumes" that come off of gold (as if there were even a gap or tunnel or fissure, in the first place , from the object to the surface of the ground !)
