I agree on the wearability of granite by wagon wheels being an improvement 
over bluestone. 

I've moved plenty of sidewalk stones already that I know I don't want to do 
it no more. I've never found a vault spanning granite in Manhattan over 8" in 
thickness, quite often at 6" thickness. Ivan's 16" to 20" seems a bit thick 
to me, but then, Ivan gets to explore some nifty places, despite his request 
to avoid BP. 

Bluestone, a sandstone, is in several respects easier to quarry than granite: 
laminar sedimentary stone lifts in sheets from the bed, and is less expensive 
as a result. You can quarry it with a crow bar, a hammer & chisel, and a 
hydraulic jack. Machines do narrow the differences in quarry cost between 
granite and sandstone. 

I have little practical faith in slabs of bluestone being used for spanning 
large areas. I have more faith in slate. I doubt very much that bluestone 
would be often used for spanning of vaults, though I have seen it used in 
townhouse stair landings where it forms a roof over the entry area to the 
lower floor. I've seen this done with brownstone, limestone and marble as 
well. These are relatively small areas being spanned. Even then I've never 
seen anything 16" to 20" in thickness. 

Contemporary bluestone comes in modular rectangular units that are designed 
to fit together with a 3/8" - 1/2" mortar joint when laid out flat in a patio 
pattern. They come in 1" to 2" thickness. You can get it in a uniform 
thickness, the more expensive because either a higher quality of stone or 
more "worked", but most often a single unit will have a varied thickness. 
These units are of a size that a single mason can move around without getting 
a hernia. They also fit on pallets fairly well, which can be moved with a 
fork lift - easier on the highway transportation than large slabs. People 
also like to set their sidewalk stones with mortar on a concrete bed these 
days, whereas the larger slabs are usually set on a sand bed - which seems to 
be a lost art in itself. 

There is no current market for larger pieces of bluestone other than for 
restoration purposes, so likewise there are no quarriers waiting breathless 
for the BP preservationeer to call. The one bluestone quarrier that I know 
personal is likely not to answer the phone at all. 

The bluestone quarriers in the 1970's in the Deposit, NY area (West of the 
Hudson, southwest of the Catskills, off Rt. 17 prior to Binghamton, not to 
far from PA), were small family operations. When OSHA came along the quarries 
were hit with a need to capitalize to purchase new SAFE equipment. Unable to 
get the capital many of the quarries went out of business. Once a quarry goes 
out of business the neighbors are very ornery about letting it open up again. 
Those quarries that remain in business have a rough time of it… it is not as 
if they are mining gold, and for the most part they have to make due with 
what equipment they have at hand. 

I'm talking about fabrication equipment, as in large saws… of which there is 
an interesting variety in the stone business. It is a comparable situation to 
a family farmer having to pay for a John Deere harvester. 

These are some of the reasons why there is a lack of equipment, as Ivan 
mentions, for fabrication of large bluestone slabs. Yes, the stone is there 
in the ground, but if you can get it out and get it cut in large sections 
good luck. There are rumors that there be a few quarries and fabricators that 
can deliver large pieces, but you have to know the secret handshake.

Merrill is a great resource on stone quarry history and if I could find one 
I'd buy it. Last time I saw one was 25 years ago in a college library. I 
copied a lot of the charts and will see if I can dig any of them out of the 
pile.

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