Frontiers in Mineral Identification: Rendering Your Laboratory Obsolete?

One of my diversions in the past few years has been teaching myself how to do chemical analysis of mineral specimens in my collection. With the correct reagents, some glassware, acids, and a decent burner, it’s possible to tease out a lot of the fundamentals of a mineral’s chemistry just by performing various procedures and observing the results. Books like Orsino Smith’s Chemical Analysis and Determination of Minerals give a sense of the state of the art dating to the 19th century. When you move beyond the basic physical properties of minerals, this can be an enormous aid in identification (about which topic I’ll write more in a later entry).

In the 21st Century, of course, these methods of chemical analysis seem somewhat quaint, somewhat dated. And with the advent of X-ray fluorescence analyzers, these techniques may well seem positively mediaeval. Or will they?

An XRF scanner in use, from the Thermo Scientific website.

As discussed in the most recent issue of Rock & Gem magazine (September, 2010) by noted author Stephen Voynick, the advantages of the new generation of hand-held X-ray fluorescence (XRF) scanners are speed, portability, and ease of use. XRF devices take advantage of the fact that when an X-ray strikes an atom, electrons are dislodged, and in order to regain electrical stability, the electrons are replaced by other electrons which release fluorescent X-rays, the energies and frequencies of which are unique to each element. With the appropriate detector, these energies and their frequencies can be measured – that’s where the XRF scanner comes in (please read Voynick’s article for a more detailed description – link to follow when it’s available online).

Of course, there’s a price for such technological advancement – in this case, an individual unit from Thermo Scientific‘s Niton Analyzers range, sells for about $42,000. Which means that, while undoubtedly useful, my home laboratory is still substantially cheaper. And the units do have their limitations – the model tested by Voynick, calibrated for geochemical analysis, could identify only 29 elements, and nothing lighter than chlorine (atomic number 17). Not that having an instant analysis of the percentage of heavier metals in a sample is anything to sniff at. But obviously, it would be hoped that as the price drops, the number of elements readily identifiable will increase.

It’s not really a choice, of course – not for me. I’ll continue to work on identification in the traditional way: hardness tests, specific gravity, streak, chemistry… but eventually, who knows? XRF scanners could eventually become an invaluable part of hobbyist mineralogy. In the meantime, there’s still the pleasure of spending time looking at something interesting and trying to figure out just what it is… After all, that’s why most of us started out in this hobby.