Also known as Colombianites and Arizonaites, Amerikanites are in fact terrestrial obsidian. Amerikanites can also be spelt as Americanites, but are not to be confused with the North American, 35 myo, strewnfield. The interesting point about these pseudo-tektites is that the sculpture is very comparable to that seen on tektites. This could be taken as evidence that the sculpture on tektites is not primary. Personally I do not think that this is the case, although I would concede that some weathering is present on certain tektites.
ABOVE: Amerikanites (not true tektites). The top row is Healdsburg Glass from California and the bottom row is Safford Glass from Arizona. A 23mm diameter Euro coin is provided for scale. Image courtesy of Brian Burrer.