Worth and Selden Quarries (Victoria Quarry), East Hampton (Chatham), Middlesex County, Connecticut, USAi

Regional Level Types
Worth and Selden Quarries (Victoria Quarry)	Group of Quarries
East Hampton (Chatham)	Quarry
Middlesex County	County
Connecticut	State
USA	Country

The Worth Spar Co., of Cobalt, has owned and operated the property since August 1942, and has been engaged partly in prospecting for sheet mica, but chiefly in mining feldspar for use in floor-cleaning compound. Four opencuts in two pegmatites have been made on the property. The pegmatites are enclosed concordantly in quartz-mica schists and mica gneiss of the Bolton schist.

Three of the opencuts are in the west pegmatite, a tabular body about 25 feet thick that strikes N. 27° W. and dips about 70° E. The pegmatite can be traced for at least 800 feet along strike. In the southernmost quarry its keel seems to plunge north at a low angle. The pegmatite is a varied mixture of [microcline] perthite, graphic granite, [albite] plagioclase, and smoky quartz, with accessory muscovite, biotite, garnet, tourmaline, and rare beryl. The muscovite is amber, clear, and hard. The books are mostly less than 4 inches broad and are commonly cross fractured. They are sparsely scattered through the central part of the pegmatite. The mica is largely scrap, but some small sheet mica has been obtained. Some coarse [microcline] perthite and graphic granite is found, but most of the feldspar produced is intergrown with other minerals.

The East Selden prospect...consists of an irregular opencut. It is in a pegmatite lens that strikes N. 25° W., dips about 70° E. and seems to plunge southward. The lens is about 200 feet long and has a maximum thickness of 34 feet. At the north end its keel is exposed; its plunge is uncertain. At the south end, the enclosing schist extends partly over the pegmatite, and the crest seems to plunge southward at an angle of 20°-30°. The contacts show sharp rolls. Those at the south end of the deposit plunge south. The most conspicuous roll, however, exposed along the footwall at the north rim of the cut, plunges N. 35° W. at an angle of 40°. A thin, steeply dipping basic dike cuts the pegmatite south of the opencut.

The pegmatite consists of quartz, [albite] plagioclase, and muscovite, with subordinate [microcline] perthite, and accessory beryl, garnet, tourmaline, and columbite-tantalite(?). Quartz is the most abundant mineral. The pegmatite is poorly zoned. The border zone, 1 to 6 inches thick, consists of quartz, muscovite, and [albite] plagioclase. Inside this is a wall zone consisting of fine- to medium-grained quartz, muscovite, and [albite] plagioclase, in highly varied proportions, with minor amounts of [microcline] perthite and accessory beryl, garnet, and tourmaline. Unevenly scattered through this are pods of coarse quartz, [microcline] perthite, [albite] plagioclase, muscovite, and beryl. The largest pod lies under the roll at the north rim of the quarry, but prior to mining both roll and pod extended 25 feet south along the headwall. The pod was about 8 feet by 6 feet in maximum cross-section. Beryl, feldspar, and muscovite were concentrated in a zone around the margins of the pod. Similar, but smaller pods were found just east of the opencut, at the north end of the pegmatite, and south of the trap dike that cuts the pegmatite.

In the north end of the lens, along parts of the foot-wall and along the hanging wall near the keel, the part of the wall zone 1 to 3 feet from the wall is notably richer in beryl than elsewhere. No distinct beryl-bearing zone can be traced at present, but it might be possible to do so if the exposures were less obscured by lichens. Along the hanging wall near the keel, some of the beryl crystals extend inward from the contact, increasing in size toward the center of the pegmatite.

Book mica from the pods, the only source of sheet mica in the pegmatite, is amber, hard muscovite, clear or stained with rust. Some books contain tourmaline inclusions. Cross-fractures, “A” structure, and ruling are common defects, but some sheet is reported to have been obtained. Books up to 12 by 8 by 2 inches are numerous around some pods, but the pods are small and sparsely scattered. The average content of book mica large enough to yield sheets is very low for the pegmatite as a whole.

Beryl forms light-green to white, sharp-edged crystals ranging from 1 inch long and 1/8 inch in diameter to 10 inches long and 3 inches in diameter. The larger crystals are zoned. Some show intergrowth with feldspar and quartz, but most seem pure. In an attempt to determine the average beryl content of the pegmatite, the beryl crystals visible in 722 square feet of exposures were measured. On this basis, the average beryl content is estimated at 0.34 percent and inferred reserves of beryl for every 12 feet the pegmatite extends in depth with its surface dimensions would be 15.7 tons. The estimate is open to two objections. First, a considerable part of the beryl is associated with pods along the footwall, and there is no basis for predicting the size, beryl content, or abundance of pods in depth. Second, another large part of the beryl is in the part of the pegmatite along the footwall. Owing to the distribution and condition of the exposures, most of the surfaces measured were in the footwall half of the pegmatite, and a thorough sampling of the full width of the pegmatite was impossible. If the part of the pegmatite lying within 5 feet of the footwall is taken, the average beryl content indicated by crystal measurements is 0.48 percent. On this basis, inferred reserves for every 12 feet this part of the pegmatite extends into depth would be approximately 4.8 tons.

Reserves of high-grade feldspar in the deposit appear small. Columbite-tantalite(?) is present in minute, rare crystals.