Beauregard Mine, Alstead, Cheshire County, New Hampshire, USAi

Regional Level Types
Beauregard Mine	Mine
Alstead	- not defined -
Cheshire County	County
New Hampshire	State
USA	Country

The mine was operated intermittently in the early 1900's, and was worked for mica by H. E. Boynton, Keene, during a 6-months period in 1936-37. It was idle until September 1943, when Arthur Whitcomb, Keene, made an operating agreement with [mineral rights owner O. E.] Cain and mined mica until December 1943. The mine is a northwest-trending open pit 90 feet long, 20 to 40 feet wide, and 15 to 40 feet deep. The northwest half of the pit was excavated by Whitcomb. Four small open pits and prospect trenches have been made near the main pit...

The pegmatite mined in the open pit is 320 feet long and 10 to 80 feet wide. It strikes N. 15 degrees E. and dips 60 degrees E. It has a narrow border zone or aplitic materiel and a wall zone, about 3 feet thick, that contains quartz, [albite] plagioclase, [microcline] perthite, muscovite, black tourmaline, garnet and [fluor]apatite. The wall zone grades into a core that is about 30 feet thick and is composed of coarse-grained quartz, cleavelandite, and minor quantities of [microcline] perthite. Beryl occurs in the quartz-rich parts of the wall zone and core. The many small beryl crystals are green or yellowish-green and have been replaced in part by cleavelandite.

In 1943 most of the mica was recovered from the wall zone along the northwest contact, or footwall. Earlier production was from small fracture-controlled units and disseminated deposits in the quartz-rich parts of the body. The mica content of the footwall part of the wall zone was high. The mica is ruby and fairly flat, but a large proportion is marred by reeves and "A" structure. Inclusions of garnet, quartz, tourmaline and [fluor]apatite are common. Most books are less than 8 inches in diameter. The mica yielded an unsatisfactory percentage of sheet, and the beryl crystals were considered too small for recovery by hand cobbing.