But because it flowed out of the volcano like a river, it's very dense. Its sharp edges have led many people of the past to make tools and weapons from it. Basalt is the most common form of cooled lava. Basalt can form in widespread lava flows, and can be seen in many locations across the globe. In India, a gigantic basalt flow covers over 250,000 square miles.
Granite is made of magma that cooled while still deep underground.
Many crystals formed as the magma cooled, so granite is speckled with mineral crystals like quartz, feldspar and mica. Granite forms in underground magma chambers that are later exposed by the weather, so you can find it throughout the world. And ancient volcanoes may have left obsidian or pumice in your area.