Tektites are very unique in that they form when a meteorite melts the earth that it comes in contact with. Often, this is in the form of molten rock and sand turned molten from the heat of impact, and may be tossed into the air, raining down as a natural glass. Tektites are named from their locations, i.e. moldavite is from the Moldau river area of the Czech Republic. Common colors of this natural glass are yellow, green, gray to black, and colorless.