Geology

The rock at the Crusher is not granite. It is actually what is referred to as “Trap Rock”. Trap rock is a dark-colored igneous rock that is very hard and brittle. It works great for construction since it crushes easily and the sharp edges lock together well in roads and similar projects, including surrounding the nearby sewer line, or “The Dike”. Most people have heard of the granite quarries of Quincy, yet most people don't know anything about our excellent trap rock which was used in many roads and buildings. "Trap rock is not a geological term that you are likely to learn about in your everyday geology course or textbook." (Trap rock, 2018) Instead, this is a term used in construction. There are two large deposits of trap rock in Quincy, Houghs Neck and South Quincy.