Want to Know Exactly What's in Those Rocks of Yours? Here's How...
(Damn! Wish I knew what was in this here rock of mine.)
As a former engineering technologist (now retired) at Los Alamos National Laboratory (LANL) I am very familiar with various types of metallurgical tests and associated testing procedures and the equipment used for conducting those tests. In case some of you don't know LANL is the birth place of the first atomic bomb, perhaps a questionable achievement depending what side of the fence you're on. As for me I never had a problem with that. It was what it was back then and deemed necessary to bring the Japanese to the peace table in 1945. That said, it is my sincerest hope nuclear weapons are NEVER used again in this world...or any other for that matter. Although weapons research is still a prime motivator at LANL, it isn't a bomb factory as many liberals and the ignorantly uninformed assume and claim. The last bomb factory in the U.S. arsenal was the Rocky Flats Plant in Colorado which is no longer in operation. Anyhoo, on to the subject at hand.
One of the methods for determining the chemical and elemental composition of various materials is X-Ray Fluorescence or XRF spectrometry. I won't go into a engineering discourse on the science of using XRF for analyzing material composition but here's the basic gist. Essentially, XRF uses the emission of high-energy X-Rays to create a fluorescent ("secondary") emission from the material the high-energy X-Rays are "aimed" at. With the appropriate data gathering gear these emissions can be interpreted and registered in terms of their chemical and elemental (including metallic) composition. XRF is widely used today in all sorts of industries to determine a material's constituents, including metals production and forming, building materials, forensics, and YES...the mining industry. Voila! There you have it. A highly accurate (about 99.9 percent) means of determining the constituents of any given material.
(Shooting a strip of metal to determine its elemental constituents.)
A "Non-Destructive" Approach
In days past XRF technology was quite cumbersome, requiring large bulky units that were installed within a facility and that required material samples be brought to them for analysis. Although fixed XRF units are still widely used today there is an entire new breed of hand-held, portable XRF analyzers out there. Many mining companies outfit their field geologists with these amazing units and even some small commercial mining operations use them to analyze the rock or ground they're working. By using a hand-held XRF analyzer you could, in a matter of seconds, know exactly what that rock in your hand contains in terms of minerals and/or metals. This is also what we at LANL called a "non-destructive" testing approach. You don't have to break that rock apart or crush it into powder. Just point your XRF unit at it and shoot. You could also (conceivably, anyway) shoot an XRF beam at a selected spot of bench gravels and also get a highly accurate reading of the constituents contained therein. Obviously, you can't expect a wide "scan" using a portable XRF unit and I don't know about their "depth" potential. However, X-Rays are a very high-energy form of ionizing radiation that can penetrate just about anything. Your best bet in using XRF units is in determining the constituents contained in a small or contained sample...like an individual rock. Getting the picture, are you?
(Really?! You mean I don't have to bust this rock apart?)
Very, Very Good
Many good and well-known companies produce and sell hand-held XRF scanners. These include companies like Olympus (remember their 35mm cameras?), SPECTRO, Thermofisher, Carleton, and others. I'm not entirely certain of the measurement gradients used in these hand-held units, but I know from my LANL years that we usually measured constituents in parts per-million (ppm). In order to read the data you acquire with your portable XRF analyzer you would be well served to study the periodic table of the elements. Most readouts use the standard elemental/metallic designators like Au (gold), Ag (silver), Cu (copper), Pt (platinum), and so on. If you come away with nothing else here understand that hand-held XRF units are very, very good at detecting and analyzing precious metals content in any given sample.
(An Olympus "Vanta" portable XRF analyzer.)
You Get What You Pay For
Now some of you are undoubtedly champing at the bit and ready to rush out the door or go online to buy one of these amazing units. Hold up there pard. Got a minimum of five grand to pay for an low-end unit? How about $10,000-$15,000 for a high-end unit? Yep, portable XRF units are extremely expensive but you get what you pay for, right? DO NOT BE FOOLED by online advertisements selling hand-held XRF analyzers for under a hundred dollars (USD). I saw one online the other day selling for $39.00!!! What a crock. These are toys, not scientific instruments. If you bought one and used it in the field for analysis try writing down your own guesses as to what the constituents are in that rock in your hand first. More than likely your guesses will be more accurate than those generated by that cheap piece o' crap claiming to be a real XRF analyzer. Be smart and don't get taken in a scam like this. Genuine, efficient, and highly accurate scientific instruments cost big bucks. There's no way around that fact.
Want to know if that rock in your hand contains gold? Buy yourself a portable XRF analyzer.
There it is...
(c) Jim Rocha 2017
Questions? E-mail me at firstname.lastname@example.org