
Vitreous, glassy texture: These cool almost instantaneously. Obsidian derives from rhyolitic magmas that ascend and cool too quickly to grow any crystals at all. Thus a natural glass, or vitrophyre, is formed. Image Obsidian boulder
Vitreous, glassy texture: These cool almost instantaneously. Obsidian derives from rhyolitic magmas that ascend and cool too quickly to grow any crystals at all. Thus a natural glass, or vitrophyre, is formed. Image Obsidian boulder