Bluestone & Regina Kellerman
The famous english henge is bluestone. The Catskills have some of the largest bluestone deposits in the world. 380 million year old sediment left by a massive delta formed on the western edge of the Acadian mountains in the Devonian Period. A working landscape, still working.

Times piece on the boom, from which the image above came. NYC preservation laws on bluestone sidewalks. And of course Opus 40 - in Saugerties. Brownstone care, the soft sedimentary cousin.
I had no idea that Regina Kellerman died this past May, bless her. An architectural historian of no compare.
And I never got to link this before. Hudson, yea we so happy! Welcome Marina.