mineral identification from spectrally filtered strobe light

How's this different to detecting colour, albeit with a wider frequency range?

NT

You get finer wavelength discrimination, which mostly won't help you very much.

You have to get up into the transition metals before the outer electrons are sufficiently weakly bound to have absorptions in the visible and mostly these are fairly broad absorptions because the chemical environment influences the energy levels.

IIRR Manganese has got some narrow-band absorptions due to something weird in the electron energy distribution, but googling didn't bring up a reference.

People have been looking for this kind of magic wand for quite some time now. If a spectroscopic scan scheme worked, somebody would have made a mint out of it by now.

You will also get false positives from anything that specularly reflects at whatever your chosen wavelength is. How much processing power will be on board? Some primitive pattern-matching will help eliminate regularly-shaped artificial objects that reflect at that wavelength.

If the strobe spectrum has enough UV in it you could look for many fluore scent minerals (and scorpions), but those probably aren't the minerals you' re interested in.

If you're looking for one mineral type at a time, and its reflection spec trum has more than one peak, tune your filters for those peaks (or use sync hed strobes with individual line filters per peak). That would require mult iple cameras also tuned to those peaks to eliminate single-peak false posit ives.

Mark L. Fergerson

A quick Google Images search for "mineral reflectance spectra" confirmed a niggling memory. Most such spectra have characteristic dips (not peaks), or steep bandpass edges, so it's a bit more complicated.

Mark L. Fergerson

So try it. It's easy enough to substitute the UAV with a ladder or a ledge during testing.

It isn't my expertise, but when I tried putting some UV identifiable rocks under a UV lamp, the fluorescence was virtually nothing. It was stronger than other minerals but weaker than the natural fluorescence of organic material and very much weaker than fluorescence of synthetics. I'd bet that you'd have trouble with clothing dust and organic compounds dominating the light produced.

You might need a quite strong light source i.e. a high power laser to evaporate some minerals and then analyze the spectrum, i.e. a flying gas chromatograph :-)

The LED based UV flashlights work quite well. Did you use a fluorescent UV light? I own a UV longpass filter cut at 420nm, which aids the viewing. But this is to get any glow, not necessarily identify the material. Lots of fungus on rocks that glows.

NASA flew a WB-57 to identify minerals from the air (cough cough) over Afghanistan. There is an actual NASA or USGS report on this, but you need to weed through all the conspiracy theory google hits to find it. [Of course, this is one time when a few of the nutcases were right.]

Wrong. A gas chromatograph separates the various components in a mixture of chemicals by entraining the sample as a gas in a stream of inert gas, runn ing the stream over a weakly absorbing sustrate, and relying on differentia l absorbtion to delay the various components by differeing degrees as they spend more or less time on the substrate.

A sufficiently high power laser could turn a point on the target into a ver y hot plasma, which would then radiate at particular wavelengths characteri stic of the various separate elements in the compound or compounds that had been heated to incandescence.

This would be rather like arc spectroscopy, with the high power laser repla cing the electric arc. Nothing to do with chromatography - and rather less informative, since you've no real idea of which chemical compounds had been blasted to atoms.

If the nutcases were right by coincidence, they could be right, and still nutcases, have endorsed the right answer for the wrong reasons.

Did any of the few nutcases who were right document their reasoning in enough detail to suggest that they'd reasoned their way to the right answer, rather than getting lucky?

You might be surprised to find out how sensitive and how specific optical measurements can be. With the right stimulation and the right filtering, specific compounds can be detected at ppm and even ppb levels.

NASA's observation of earth from the air and space has been going on for decades.... I have LaserDisc issues that are not even available any more of their compiled public releases at that time. There was a famous Learjet flyover at 40,000 ft taking hi res photographs of our cities long before there was ever a "Google Earth".

I have detailed spectrographs of that entire region long before there even were idiot loon conspiracy theorists.

That's not actually what a gas chromatograph does. Chromatography is about separation of a moving gaseous sample by attraction to a stationary substrate. You may be thinking of a spectrophotometer detector that is just one of many types of GC detectors used.

The original motivations were petroleum deposit zone detection improvements, and gold and Uranium deposit spotting (gold was places likely to have, and Uranium was directly observable)

Reminds me of a guy who predicted the peak output of the oil industry in about 2000. I pointed out to a friend that this guy pretty well nailed it. The friend pointed out that there was a whole spectrum of predictions by many people and someone had to win the lottery.

I'm not sure what nutcases have to do with analyzing minerals from the air. But given enough nutcases making random claims, there will sooner or later one that gets something right.

This isn't what Jamie was speculating about. If you know exactly what you are looking for, and it has the right spectal properties, you can detect ppm and perhaps ppb levels, but Jamie was talking about "reflected light signatures of rocks on the ground".

I think you have to assume that all the good stuff in easy-to-reach locations and near the surface has been found.

We're looking at stuff kilometers below the surface in absolute hell-holes.

Best regards, Spehro Pefhany

You may not like the result of looking for individual surface rocks; think BIG and look instead for mountains of unusual color

Yep, diamonds are sorted that way from crushed ore, and someone HAS made a mint, but not by looking at surface rocks in such detail. Surfaces get covered in whatever's windborne (or worse, in moss and lichen).

There is stuff I can't say.

The US already knew where the minerals were located in Afghanistan. This has been documented for decades since the Russians did much of the leg work, then the US followed up after the Russians exited. The place was studied on the ground and with remote sensing. So the mineral hunt wasn't really necessary, well unless you wanted a cover story to fly a spook plane over the country.

Even if you know what is located where, what is the next step? The trouble with mineral wealth in Afghanistan is how do you mine it? Water is scarce, There is no networks of roads. You need infrastructure to mine minerals. Even if the place wasn't a war zone, it would be hard to justify mining the place at current prices. Basically the new study wasn't warranted.