Fig. 9.

Examples of juvenile “fresh scoria” particles in vulcanian ash. Both photographs were taken under binocular microscope. For definition of “scoria” particles and its sub-types (“fresh” and “partly-altered”), see Subsection 5.1.1. (a) shows “fresh scoria (juvenile)” particles in February 18 ash (250–500 μm fraction). Some of the “fresh scoria” particles are oxidized, similar to coexisting “fresh lava” particles (Fig. 7(c)). Degree of surface luster of unoxidized particles is variable. (b) shows “scoria” particles in April 18 ash (500–1000 μm fraction). These were classified into “fresh scoria” (Table 2; Fig. 2) because of luster inside vesicles (e.g. particles with arrow) and resemblance to “fresh scoria particles” in previous eruptions (e.g. Fig. 9(a)), although surfaces of particles in (b) are abraded. Color version available online.