<a href=showthread.php?s=&postid=7538413#post7538413 target=_blank>Originally posted</a> by Unarce
Tom,
Standard glass has the obvious dark green edge, which most glass tanks are made of. Low-iron glass has a clear, ice-blue edge. Starphire is the brandname of low-iron glass by PPG Industries, which is whats mostly used in the aquarium industry because its physical properties are still close to standard glass.
Diamante glass is the next step up, where the iron is completely removed, leaving a clear edge. Low-iron and Diamante glass are both considered optical-quality glass, but the absolute clarity of Diamante is useful for microscope slides, art and jewelry making. I believe Diamante glass is pretty brittle in comparison, which is likely why it's not used to make aquariums.
HTH