Corundum -- Al2O3 Hematite Group - Sapphire is a color type gem that isn't red - ruby is red.
Other colors are sapphire - blue( star), black (star), yellow, ....
also known as corundum, magnetite, hematite, and spinel.

That is first year Mineralogy class. Useful when trading stones...

Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder



Don Stauffer wrote:
Don Bruder wrote:


The part that grabs my attention (as a wearer of corrective lenses not
in contact with the eyeball) is that whole "scratch resistance"
thing... I'm forever cussing at the cost involved in replacing a set
of glasses due to the "fog" of scratches that sooner or later collect
on my lenses, regardless of how carefully I handle them.
If this stuff can be worked into lenses, I'd be thrilled to have a set
made out of it, since it might *FINALLY* mean I'd get to look through
scratch-free lenses for more than the first few weeks after getting a
new pair...


Isn't Aluminum oxide Sapphire? Don't know what percentage of nitrogen
they are talking about, but if I remember right pure Sapphire (straight
aluminum and oxygen) are transparent- color is due to various
impurities. I know sapphire is used for infrared lenses and windows. I
see no reason similar materials cannot be used for lenses, but one must
check the dispersion charactoristics to see if result would give too
much chromatic aberration.

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