5:15 PM - 6:30 PM
[SVC48-P18] Foaming temperature and textural classification of vesicular substance by heating experiments of obsidians
Keywords:obsidian, perlite, heating experiment, foaming temperature, volcanic glass
Perlite texture was classified into three types (type-A, -B and -C) based on the diameter, morphology and number density of vesicles. Type-A has discrete spherical forms with about 1 mm in diameter, which belongs to Tf>990℃, Tp>1060℃ group. Type-B, Tf=900-930℃, Tp=1030-1060℃ group, has distorted spherical forms with 1.5 to 5.0 mm in diameter. Type C is characterized by high number density and small size of vesicles (< 0.5 mm) connecting with each other, belonging to low Tf (<890℃) and Tp (<950℃) group.
The texture of perlite made by obsidian heat experiment is different from that of natural vesicle substance such as pumice and vesiculated obsidian. Lower number density of vesicles in the experimental product perlite is due to low H2O content in quenched obsidian after degassing of H2O in obsidian magma. The difference in vesicle morphology between the spherical form of perlite and reticulated irregular-shaped vesicle of natural vesicle substance is related to the difference in the static or dynamic condition of formation environment.