Granite Mirror?

[OICURMT]

http://www.cloudynights.com/classifieds/showproduct.php?product=70906&sort=&cat=last7&page=2

I'm struggling to see how you can make a quality mirror out of granite considering the different mineral types within it all have differing coefficients of thermal expansion. Maybe if you lived in the tropic where the temperature does not change much...

Novelty item?

Comments?
OIC!

[mswhin63]

Granite mirrors are used extensively in crafting. My wife although doesn't use these she has info on it. It is possible the person used this idea to apply it to mirrors for telescopes.

One advantage is it could be used to experiment, much cheaper that getting a Pyrex blank on a new machine. If the experiment works in real life then is could be a goer for economical scopes.

I was up at the MWA site 6 months ago and they had many granite boulders there dug up from the cable channel and on the NBN rollout along the road to MWA. Would have been nice to grab a bit. The engineer mention how hard these blocks were to remove when laying the fibre.

[rcheshire]

Exfoliation? Don't leave it in the Sun?