This is a surprisingly attractive specimen of a rare serpentine group species called Antigorite, from the old Tilly Foster Mine. According to MINDAT: Large iron ore (magnetite) deposit discovered in 1810. The mine was 600 feet deep in 1879. Mining ceased in 1897, after 13 miners were killed in a rockslide. Specimens today are obviously hard to come by, and I know people who are dedicated to collecting Tilly material. Usually, you get chondrodite, and a few other species like clinochlore as mere associations. However, here it is definitely not common to get a good specimen of one of the rock-formers like this serpentine group species, that is actualy a "specimen" and not a "rock." This is a really interesting, showy, crystallized piece, with a distinct curvature to the crystals and to the specimen overall. Ex. Ken Hollman Collection