If you’re near Barre, Vermont, head to Rock of Ages. This is a massive granite quarry believed to be about 600 feet deep.
The visitor center is well done with a film on its history and samples of their granite cutting boards, headstones, and monuments.
For a $7 ticket you’ll drive with a guide up to a quarry overlook. Not only will he provide a lot of information about how the granite is removed from the quarry, but as a bonus you’ll have some great views of Vermont.
Plan to go on a weekday so that you can see the plant. The samples of craftmanship were phenomenal so it would have been fun to see the masters at work.