Bill Nelligan wrote:

> The project in question involves replacement sandstone at the Old
> Courthouse in St. Louis.  Approximately 20 yrs ago sections of damaged
> sandstone were replaced with new sandstone.  Now the replacement stone
> has deteriorated, while nearby orginal sandstone is still in good
> condition.

In Cyprus, I recently learned, they have the same problem of the more
recently quarried stone being less durable than the stone quarried at some
past historic era. Seems the resource of durable building stone has long
since been depleted, even though they continue to have deposits of
sandstone that has the appearance of the original. A problem for Cyprus in
their efforts to preserve their historic structures, many of which are
older than the ones we worry about here in America. Bear in mind,
relatively speaking in our daily terms, all stone is close enough to being
equally old. It is not a question of one stone being older than another. It
is a question of where it came out of the ground and was it durable to
begin with? Durability of stone is commonly tested by the stone industry. I
suggest you contact the Building Stone Institute for references to
qualified testing labs experienced in working with quarries.

][<en Follett