Webvolcanic glass, any glassy rock formed from lava or magma that has a chemical composition close to that of granite (quartz plus alkali feldspar). Such molten material may reach very low temperatures without … WebAug 17, 2024 · Obsidian is created when the volcano’s felsic lava cools quickly with minimal crystal growth. The chemicals (hodium silica content) produce a elevated viscosity that shapes a natural glass from lava when rapidly drying. The chemical composition is often discovered on the edges of rhyolitic lava flows recognized as obsidian flows.

Volcanic glass geology Britannica

WebPortions of this obsidian flow are mixed with layers of pumice, a glassy, bubble-rich, lightweight rock that develops when water vapor (steam) escapes rapidly from the molten glass at or near the ground surface. Sometimes obsidian of excellent quality develops as surface lava flows. WebLava will sometimes cool so quickly that not even microscopic crystals will form in it. As a result, volcanic glass will form with a shiny, smooth appearance that reflects light. This texture is called glassy . Just like the mineral quartz , a glassy rock will have conchoidal fracture with distinctive, rounded fracture edges. sharon fisher gastonia

What is obsidian? Why obsidian is black? - Geology Page

WebObsidian, or lapis obsidianus, is essentially dark glass. A type of igneous rock, called extrusive igneous rock, obsidian is extruded from the Earth as lava which when rapidly … WebObsidian, igneous rock occurring as a natural glass formed by the rapid cooling of viscous lava from volcanoes. Obsidian is extremely rich in silica (about 65 to 80 percent), is low … WebOf the cooling mechanisms responsible for forming volcanic glass, the most effective is quenching by water, followed by cooling by entrained air in an eruption column. The least … sharon fischer esthetician