The primary rocks of the county consist of gneiss, hornblende, granite, sienite, limestone, serpentine, angite and trappeau. They extend over parts of several towns, and several mountains and hills are composed of them. Granite is found at the foot of Butter Hill, sienite at Butter Hill and on the east side of Bare Mountain at West Point, gneiss along the Highlands, mica and slate north of Fort Montgomery, angite rock between West Point and Round Pond and at several points in Monroe, greenstone trap at Tuxedo Pond, granular limestone at Cro'-nest and Butter Hill. Quartz rock and hornblende are all along the Highlands and in Monroe and Warwick. Crystalline serpentine is in the white limestone in Warwick, serpolite at Amity, yellow garnet at Edenville, soapstone in Monroe. Large sheets of mica are found southwest of the Forshee iron mine in Monroe, and in this mine, which embraces an entire hill, are red garnet, brown tremoline, carbonate of copper, serpentine, cocolite and umber. In the O'Neil mine, half a mile northeast of the Forshee mine, are crystallized magnetic ore, magnetic and copper pyrites, carbonate of copper, serpentine, amianthus, asbestos, brown and rhombic spars, angite, cocolite, feldspar and mica. There are beds of arsenical and titanium ores in Warwick and a bed of hemolite ore near Canterbury village. Magnetic oxide of iron abounds in the primitive rocks of the Highlands, and at West Point is associated with hornblende. Beds of lead have been opened at Edenville and in the towns of Mt. Hope and Deer Park, and zinc and copper ores have been found in small quantities. The Sterling iron bed in Monroe, which was opened in 1781, extends over about thirty acres, and has produced so strong an ore that it has been much used in the manufacture of cannon. There are a number of other iron mines. Searches for the traditional silver, gold, lead and tin mines have been without satisfactory results. Many evidences of glacial action in Orange County include masses of boulders scattered in places throughout the county. These are mostly of granite and gneiss, and there is occasionally one of grawacke. The eastern slope of the Shawangunk Mountains gives evidence of the passage there of an enormous glacier, which ground the rocks into the rich soil that has been cultivated there for 200 years. Some of the county's drift deposits are valuable for casting, brick and pottery making, lithographic stones and glass.