This quarry was "in Muscle Ridge Plantation, 9 ½ miles south-southeast of Rockland." In 1905 the operator was William Gray & Son of Philadelphia Pennsylvania. Granite from the quarry was reportedly a slightly pinkish medium-gray color with conspicuous black mica and had a medium to coarse texture. Transport of the granite was by gravity and track 650 feet to the wharf.
The High Isle Quarry opened about 1894 and had five openings. Each of the openings were about 100 feet square and had maximum depths of 50 feet with an average depth of about 17 feet.
Granite from the High Isle Quarry was used for buildings. The bridge seats for the Pennsylvania Railroad and the Wanamaker store in Philadelphia were made from granite from this quarry.