FIGURE 1. Powder XRD scans showing the mineral phases in expanded vermiculites. (a) Two scans of differing count times of Zonolite; the 2–17° scan (with count time of 8 s) shows the three mineral phases routinely found in an expanded vermiculite product with each of the peaks labeled and keyed to hydrobiotite (hy), vermiculite (ve), and biotite (bi), and an 8.5–11.5° scan with a 180 s count over the location of the 110 amphibole peak as well as the 003 hydrobiotite peak. (b) Two stacked XRD scans of the unspiked Black Gold sample with range and count times as in Figure 1a. Notice the three mineral phases in the lower scans and that K-exchanging the sample "collapses" them into the single biotite peak, thus removing the interference of the 003 hydrobiotite peak with the 110 amphibole peak. (c) This scan is a K-exchanged sample from Libby clearly showing presence of the 110 amphibole peak.