This may help a little bit with the grist stone question.  I recall
reading somewhere that the conglomerate rock of the Shawangunk Mountains
was used to manufacture grist stones in the colonial period, but that the
industry declined at the end of the eighteenth century because of the
widespread importation of superior grist stones from France.  This seems to
hint at a pattern--use of local sources in the early colonial period with
replacement by imports as the colonies became more prosperous.

David Allen