THANKS!!
i tend to leave them a bit course on the back...
its an interesting question whether polished surfaces are harder to crack, or rough ones.
you can make cogent arguments on both sides...
It gets even more complicated once one factors in varying internal structures, water, etc...
the main reason i don't do it is for the same reason glass loses light out the back and frosted glass doesn't
basically superstition...
given that none of us tested this, and no of nothing on it, we are stuck with beliefs and superstition
though don't knock it as people who work with things for long time have intuitions that are great even if they cant formulate what they are doing in a way that math men like me could do something with it. at least i am not like others that claim cause i don't know they don't, its just different knowing, when it works and is confirmed (otherwise its a belief of knowing, not the same thing as beliefs are more real than real - meaning they trump real).
wish i had the time to actually do a test with an opal... i have tons of junk that would be ok for a test..
but first it has to be formulated and thats not easy... (bad science can look like good science i form, and its hard to tell them apart without some deep thinking on how things are set up and the claims one wants... i see some of the worst coming from weather area under politics, and social sciences for the same area, politics... )
one really would have to create a set up in which the mechanism of light measure would stay fixed relative to the stone
so i guess one would have to start with a polished stone all around, mount it with the bottom accessible in the mount, mount the light, mount the sensor, and make that all fixed... then put it in a container to restrict all other light, then measure... remove the item, and then sand the bottom of the stone (dry as wet would change the nature of the rest of the stone), and then repeat the measurement...
i would bet that there would be more light on the frosted one, however i would also bet that it is so small that it means nothing (given surface area, vs transmission vs reflection).
just thinking outloud... sorry...
and it's amazing what good welo can survive 
... oh, but i am 
... oops 
... snik... tic tic tic tic... 
k... onto the wood floor 
... tic tick tic... 
