I would recommend that you strive to take this tour when the quarry is in operation (i.e., Monday-Friday in the Spring through Fall. The quarry shuts down during the worst part of the winter.). If you watch the video in the visitors center before beginning the tour, it will help get you acclimated to the quarrying process so you'll appreciate what you're about to see.

The tour of the granite quarry is via a school bus which drives past the factory buildings while the guide tells you what activities occur in each building. There is one stop at the quarry where you can disembark and take pictures and see the quarry in action. From the edge of the quarry, the guide pointed out the pieces of equipment and what their function was and gave interesting trivia about the operation (for example, at their current rate of production it will take 4500 years to exhaust the supply of granite in the quarry).

After the bus ride, you can take a self-guided walking tour of one part of the factory. Unfortunately, you are limited to a catwalk elevated at one end of the building so you can't see everything that you might like. Binoculars help, though.

The tour guide was knowledgeable, personable and encouraged questions from the audience. I considered it time and money well-spent and would recommend the tour to others.