While this is not a biblical source, according to an article on the Freemason website yorkriteofcalifornia.org,
Foundation Stones, Cornerstone Ceremonies and other Masonic Stones
Submitted by Jerrold A. Wohlfarth
Grand High Priest 2007/2008
Grand Chapter of Royal Arch Masons of California
the following is said of a cornerstone in ancient times:
"We know that the cornerstone, or foundation stone, of an edifice in ancient times was a perfectly squared stone from which the remainder of the building could be plumbed, squared and leveled. It provided the builder a point of departure, or reference, which insured that the structure would be properly built. If the first stone, the foundation stone, or cornerstone was not plumb, square, and level, the error would become more and more exaggerated the further the builder went from that corner stone. We know that examination of still standing structures built in ancient times disclose the perfection and exactness required of the stonemasons who constructed the buildings of the time. The stones had to be perfect."
While this does not say anything about the composition of the stone it does address it's attributes and Masons would certainly be a good source of information.