Figure 2
Al 2 O 3 vs. SiO 2 (wt. %) for prismatic and platy cristobalite, and devitrified and magmatic quartz. Data derived from electron microprobe analyses of individual crystals for all dome-rock samples. No data for devitrification cristobalite as ‘feathery’ crystals were too small for the resolution of the microprobe.