A tektite is a naturally-occurring piece of
glass, probably formed by the
impact of a large
meteorite on the Earth's surface. Tektites are usually dark in color, resembling
obsidian. They're considerably rarer than meteorites and are only found in a few locations. There is also an older theory suggesting that tektites originated on the
moon; but analysis of their chemical composition, along with comparison to lunar rocks, gives strong evidence of
terrestrial origin.
Assuming the meteorite-impact theory is correct, the ground at the point of a large meteorite impact is suddenly heated to above its melting point. Bits of liquid rock fly through the air, spinning and solidifying into tektites with unusual, aerodynamic shapes. Tektites' unusual shapes, combined with their scarcity and exotic origin, make them popular with collectors. Different vareties of tektites are named according to their place of origin. (Indochinites, Australites, etc.)
Tektites were also the weird spidery creatures in The Legend of Zelda.