SAMPLE PREPARATION DECISION TREE
[You already have a polished thin-section of your sample.]
This is not the ideal situation because top-mounting mineral standard grains on a polished thin-section is difficult and risks shattering the sample. One potential work-around is to use two separate mounts during your analytical session, one containing standard grains and the other your polished thin-section. This is not the ideal analytical procedure and you will lose analytical time while regularly switching between sample/standard mounts, but you avoid the risk of shattering your sample or polishing it away during top-mounting. This decision will be yours to make, please contact the lab to further discuss your options.
Proceed only if unavoidable, otherwise please follow instructions for making custom thin-sections for WiscSIMS analysis.
Hopefully your analytical target is near the center of the thin-section so that you can cut a 1-inch round from the thin-section and still have the target be within the 16 mm-diameter "sweet spot" when mounted in the sample holder.
If this is the case, then you'll need to cut a 1-inch square from your thin-section with your target in the center, and either cut or grind the corners off to create a circular thin-section. Then, you'll need to top-mount your mineral standards on the circular thin-section (within the "sweet spot" diameter).
If a 1-inch circular thin-section is not feasible, then you'll need to cut out the area of interest from your thin-section and treat it like a pre-polished surface for mounting in an epoxy grainmount (you won't have to top-mount your mineral standards). Switch branches of the decision tree and cast your thin-section fragment in epoxy (link).