Markham Mica Quarry, Hog Hill, East Hampton (Chatham), Middlesex County, Connecticut, USAi

Regional Level Types
Markham Mica Quarry	Quarry
Hog Hill	Hill
East Hampton (Chatham)	Quarry
Middlesex County	County
Connecticut	State
USA	Country

The Markham mica mine lies in the town of East Hampton, 1.5 miles S. 45° E. of the village of Cobalt. From Cobalt travel 0.8 mile east on U. S. Route 6 to the Colchester road; proceed east on this road for 0.4 mile; turn southward on a gravel road that leads 1.3 miles to the deposit. The workings lie in rolling woodlands, about 100 feet east of the gravel road.

The property is owned by Mrs. Grace Markham and her two sons. Mining was started by Peter Armando, of Glastonbury, and Romano Milanese, of Higganum, who leased the property and operated it intermittently from November 1943 to April 1944. In March 1944, when examined by V. E. Shainin, the working was an open pit 25 feet long, 12 feet wide, and 14 feet in average depth. The long axis of the cut had a trend of N. 65° W.

The opencut is in an irregular pegmatite that strikes N. 30° E. and dips 65° NW. The pegmatite is exposed only in the cut. It is about 20 feet thick, and is concordant with the foliation of the enclosing medium-grained quartz-mica schist (Bolton schist). Two schist screens lie 4 to 6 feet below the ground surface. The screens are roughly parallel to the walls of the pegmatite, extend across the width of the opencut, and each is about 2 feet thick.

The pegmatite is composed chiefly of quartz and [microcline] perthite; it possesses a border zone and core. The border zone is 1 to 6 inches thick and consists of fine-grained quartz, plagioclase [albite], and muscovite. Essential minerals in the core are medium- to coarse-grained quartz, [microcline] perthite and muscovite. Garnet [most likely almandine], tourmaline [schorl], biotite [annite] and apatite [fluorapatite] are accessories.

The pegmatite is a disseminated mica deposit. Hard, pale green and pale ruby mica occurs in scattered books that range from ½ to 4 inches in diameter and average 2 to 3 inches in diameter. The books are heavily intergrown with tourmaline, feldspar, and quartz, and probably contain less than 1 percent of sheet mica. Common defects are “A” structure, reeving, limonite-staining and cross-fracturing. Subhedral inclusions of flattened tourmaline are common; ruling and wedging are present, but are uncommon.

The workings were abandoned because the percentage of mica in rock moved was low and the content of sheet mica in mine-run mica was low. The exposed part of the pegmatite is unpromising as a source of sheet mica, and it is unlikely that a better deposit exists at depth.