Figure 4.

(a) Grain size distribution and (b–d) mineralogical componentry of the isolated respirable volcanic ash sample from the August 2006 Tungurahua eruption. (b) Number proportion of phases assessed by discrete Raman spectroscopy analyses on 133 individual grains. (c–d) Raman spectra for all the mineralogical and carbonaceous phases identified in the sample (vertical axis is arbitrary unit). Accessory phases rutile, olivine, and carbonaceous matter each comprise less than 1 number % of the sample and are excluded from (b).