Volcanic glass was widely known and highly prized around the world in ancient times, particularly for it's use in making exceedingly sharp-edged knives and blades. For example, archeologists in Hawaii have discovered numerous examples of birds that have been cut up with obsidian blades.
The quality of obsidian - volcanic glass - found in Hawaii is not nearly as good as that found in Mexico, for instance, but the Hawaiians nevertheless decided that what they did have was very useful. Most of the usable Hawaiian volcanic glass apparently took the form of rope lava, as shown here.
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