Monte Arci was one of the most important Mediterranean centres for mining and processing of this volcanic glass in the area.
22.
Obsidian, a naturally occurring volcanic glass, can also be used to make sharp glass knives; obsidian surgical scalpels are available commercially.
23.
"' Perlite "'is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian.
24.
A portion of the southwestern flank of Mount Fee comprises no volcanic glass, but rather composed of an abnormal cryptocrystalline matrix.
25.
Soils with duripans are often geographically associated with areas of volcanic activity, and show evidence of ash or volcanic glass deposition.
26.
Although such bladed tools were often made of stone, naturally occurring glasses such as obsidian, natural volcanic glass, were also commonly used.
27.
Products of this rhyolitic eruption are pumice and obsidian, the volcanic glass that Native Americans used to make arrow points and scrapers.
28.
It commonly occurs as a devitrification product of volcanic glass shards in tuff and as vesicle fillings in basalts, andesites and rhyolites.
29.
This rock is grey-bluish and contains anorthite ( labradorite kind ) and hornblendes trapped in volcanic glass comprising feldspar, pyroxene and olivine microlithes.
30.
The dacite volcanics composing Mount Fee contain brown volcanic glass as much as 70 % and vesicular textures as much as 15 %.
