Yes Joey I believe so but can't prove it.
I know one thing though. When I was in Boy Scouts and we had winter camporeee we threw a brick in the fire and then wrapped it up in a towel and put it in the bottom of our sleeping bag to keep warm. Temp got into the teens that night and my brick stayed warm most of the night. So yeah they hold heat pretty well I would say.
[Edited by Steve Wiggins on 10-17-2005 at 05:15 PM]