Astro Ready Mix is yet another stone customer, though everything I know about their operation I learned here. They are unique in that they unload cars off-site, on the spur for a nearby warehouse. There is video on YouTube of the siding being switched.
There's also another rock "terminal" on the Central branch. So, that's now six operations receiving aggregates via NYAR.
A lot of rock comes from Tilcon, which has quarries all over CT. One of their quarries has its own railroad, the Branford Steam Railroad, which sets out a lot of cars for P&W at Branford on the NEC (the rest of their traffic goes to a dock on the LI Sound and is barged across). Tilcon also has a big operation north of New Haven, on the P&W line to Middletown.
I read somewhere that there is yet another rail-shipping quarry north of New London that's run by a separate company.