A couple of additional points about the article
1. The brown sandstone used at Trinity Church and quarried in Longmeadow, Massachusetts, is the same brown sandstone quarried in Portland, Connecticut, and better known as the brownstone used throughout the east coast.
2. The Keystone Building, which has travertine panels, has had some maintenance issues in the past. Many of the panels have had to be replaced or reattached because water has gotten into the stone and frozen and cracked it. This occurs commonly with travertine, if used in colder climates.
3. As noted in the story, the Aquia Creek sandstone used at the St. Paul's has suffered a bit. If you go up to the columns you can see how many times they have had to be repaired.
4. In regard to the slate at Memorial Hall and the colors, the article needs a bit of a clarification. Oxygen does color the stone green or purplish but there was less oxygen in that environment relative to the amount of oxygen that fostered the red slate.