I have cleaned hundereds of gemstones (mostly cabochons) with Dow
Corning "Sight Savers" and have not scratched one. I think there
may be some confusiion over the words Silocone and Silicon. Silicon
is a metalic element and could scratch some materials. Silicone is
a chemical compound that is used as a lubricant. In fact is is so
slick that it can be used on the Space program Shuttles and other
objects operating at sub-zero conditions. Sight Savers are slick.
And they will scratch your eyeglasses. Ask an optician!