NOTE: The ideal sample is as coarse in grain size as possible. After irradiation very fine grained separates become radioactive powder and present serious concerns for contamination in the lab.

The general rule is that the coarsest size fraction which can be separated from your rock without composite (multi-mineralic) grains is desirable. Coarse material is easier to handle and less dangerous after it has been irradiated. Pure mineral separates are critical. Coarse-grained samples may often be most easily separated by hand picking under a binocular microscope. Samples separated using heavy liquids such as bromoform must be rinsed thoroughly in acetone afterwards to avoid potential contamination of our vacuum system. Zapping the mineral separates in acetone followed by distilled water in an ultrasonic bath will aid in final cleanup also. We need approximately 50-100 mg of a typical mineral separate for analysis. Amphiboles (~3.1-3.3 specific gravity or G) can typically be separated by settling out of heavy liquid with a G of ~3.10-3.15 whereas muscovite and biotite (see below) will float. A permanent magnet passed over the amphibole separate will remove magnetite. Final purification is usually done by hand picking. Beware of biotite inclusions in your hornblende! In many rocks a good size fraction for amphiboles is ~100-200 µm.