[thackney]

Transparent Aluminum (Aluminum Oxide)

You might not like the price or the weight for your eyeglasses. Double the density compared to the same index of refraction.

http://www.eyeglasslenses.com/content/knowledgebase/kb_materialsandtypes.asp

http://www.mt-berlin.com/frames_cryst/descriptions/sapphire.htm

[martin_fierro]