Derek's comments about the likelihood of better cohesion of granite than
bluestone, which certainly makes sense as there is no grain in granite to
delaminate, does seem to contradict the numbers given for the modus of
rupture which rates granite and sandstone as more or less equivalent.  This
shows the difficulty of determining quantifiable characteristics for natural
materials.

One thought about the use of granite in Soho.   Not only is there the need
to span the vaults which do not normally lie under residential sidewalks but
these stones abut the loading docks of the warehouse structures.  It is
possible that the additional loading and wear from iron-bound wagon wheels
would have been too great for bluestone.  I have studied the wear patterns
on the tooled surfaces which were originally textured so that they wouldn't
be as damned slippery when wet as they are now.  If I remember correctly the
tooling tends to remain more intact close to the building lines and away
from the loading areas.  In Pompeii you can see where the stones laid as
cross walks within the open gutters that ran through the middle of the
streets are deeply rutted by wagon wheels.

As to bluestone pavers, the ones in front of the NYU Institute of Fine Arts,
(Duke Mansion) on E 78th off Fifth are the largest and finest I've seen.
There is one slab in front of the entrance that must be 12' X 16' and no
cracks.  I don't think its over a vault.