As with other forms of obsidian, rainbow obsidian is both rock and glass ... 20 million years ago – and the same goes for ...

Extrusive igneous rocks are formed by magma that has erupted onto the surface as lava and then cooled quickly. Obsidian is an example of an extrusive igneous rock. Obsidian has crystals which are ...

Here are few interesting details regarding the formation and types of these ... to contain gas bubbles. Obsidian, Rhyolite and Granite are all examples of igneous rocks. Metamorphic rocks are ...

Obsidian is formed, in particular, by explosive volcanoes, not the tranquil types found in Hawaii. Its essential ingredient is the thick, gooey molten rock, or magma, that lies below these ...

An amazing variety of rocks appear in Hawaii from a single type of molten rock called basalt ... filled with steam shatter in the waves. Obsidian is quickly-chilled lava, cooled so fast its ...