The world’s largest granite quarries, 4 miles southeast of Barre off I-89 exit 6, cover 50 acres. The granite vein that’s mined here is a whopping 6 miles long, 4 miles wide and 10 miles deep. The beautiful, durable, granular stone, formed more than 330 million years ago, is used for tombstones, building facades, monuments, curbstones and tabletops. From the onsite Rock of Ages Visitor Center there's a quarry tour which includes a short video and historical exhibits. This 35-minute guided minibus tour of an active quarry heads off-site. At the onsite Rock of Ages Manufacturing Division, you can watch granite products being made – some with an accuracy that approaches 25-millionths of an inch.