Occasionally you have a professional experience that is just too good not to share. I recently attended a three day SIMS (secondary ion mass spectroscopy) workshop at Arizona State University in Tempe and I was extremely impressed by the experience which was an excellent balance of theory and pratice. ASU has a Cameca 3F unit, a 6F machine and a new Nano SIMS 50L. SIMS is among the most sensitive analytical techniques used principally in surface analysis for trace element work to the ppb level, isotope ratio determinations and diffusion (depth profiling) studies as well as geochronology. Led by Linda William, Rick Hervig, Peter Williams and Klaus Franzig, after a day of theory the group, limited to twelve, was split in two for simultaneous hands on time on the 3F & 6F units. The hands on time doing relevant analysis work was invaluable and while there is the possibility of a neophyte wreaking real havoc with the instrument the expert guidance provided had us all feeling relatively comfortable with the experience quite quickly.

SIMS instrumentation and analytical methodology is the most complex analytical instrument procedure out there, but it is equally powerful. The staff could answer any question posed and were incredibly informative and personable making it a great experience for all the participants. There was no cost for the workshop and a travel stipend was provided. Unlike the UCLA workshop the ASU event embraces both professionals and students and I would not be capable of giving it a higher recommendation.

The major users of SIMS worldwide are from the semi-conductor industry but SIMS work is highly applicable to geology as well. The professional literature is full of work by geologists where SIMS is the primary investigative technique.

While EPMA (electron probe microanalysis) is still the “go-to” technique for a full quantitative chemical analysis it does have limitations, one of the most noticeable is its inability to analyze light elements (H, He, Li, Be & sometimes B). Plus, the limits of detection for trace elements is usually about 100 ppm.  So, if you were to use the microprobe to analyze tourmaline or Kunzite you could do a second analysis with SIMS to quantify the beryllium and boron in tourmaline and the lithium in kunzite.

One of the sticky problems in gemology at the moment is Be treatment of sapphire. New techniques are reducing the quantity of Be necessary for color enhancement down to 5-10 ppm. This is close to the limits of detection for LIBS (laser induced break-down spectroscopy) which is semi-quantitative anyway, so either LA-ICP-MS (laser ablation inductively coupled plasma mass spectroscopy) or SIMS are the preferred methods to quantitatively determine Be content. If you were interested in diffusion studies SIMS could give you a very accurate chemical profile of Be through the stone, assuming you cut the stone in half and analyzed the profile.

Other areas of interest would be trace element determinations and isotope ratios. Larger SIMS instruments like the Cameca 1280 are capable of very accurate geochronology work, so if you wanted to characterize the age of zircon or monazite inclusions, that would be possible. Geologists are also making interesting assessments and discoveries with isotope ratios which is another strong-suite for SIMS.

Nano SIMS, done with the $5.5 million Cameca 50L, is among the most sensitive analytical techniques in the world today but the downside is that any SIMS unit is a remarkably complex instrument with complex analytical methodologies. The mass interference issues alone are mind-numbing. The number of SIMS instruments far exceeds the number of experienced SIMS operators for whom the job market is excellent. I am not joking when I observe that it would take about 10 years of experience for an operator to become fully acquainted with the instrument and all the varied techniques.

More information on SIMS will be available in the Instruments section.

The 6F represents a more automated, relatively recent unit.

The Cameca 3F is an older less automated workhorse of a unit.

The $5.5 million new Nano SIMS 50L in the process of being installed.