Brack Gem prospect (Brack prospect), East Glastonbury, Glastonbury, Hartford Co., Connecticut, USA

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Decomposed lithium-rich granite pegmatite. Unlike other pegmatites in this region, this one has completely decomposed feldspar, with "nests" of pocket contents occurring loose in soft clay. According to Jarnot (1995) it produced some of the finest colored gem elbaite and gem beryl from the state.

The "quarry" is no longer evident and only dirt dumps are obvious. Barton and Goldsmith (1968) provides a description of this weathered, gem-rich pegmatite that was hand-worked by the Brack family from 1958 to 1963 but is now abandoned:

"The Brack prospect....is on a 71-acre tract owned by Arthur and Walter Brack of East Hampton. It is a gravel pit in the crest of a residually weathered rare-alkali pegmatite. It was being worked on weekends by the owner in 1963. Workings consisted of an irregular oval pit 150 by 75 feet in plan and 5 to 10 feet deep.

The fresh pegmatite was not exposed but the weathered material appears to be approximately in its original attitude and appears to strike northeast and dip 20° to 25° NW. It is on the crest of a ridge beneath up to 5 feet of glacial sand and gravel. Weathered mica and feldspar have shown up in test pits for 300 feet along strike. Feldspar has weathered mostly to kaolin leaving lepidolite, muscovite, quartz, beryl, and tourmaline of many colors, and some rotted cleavelandite as gravel. Some of the finest beryl and watermelon tourmaline crystals ever found in New England have been recovered. The approximately 1,000 pounds of beryl and 250 pounds of tourmaline that have been hand-sorted included approximately 200 pounds of beryl and 25 pounds of tourmaline of faceting grade. A gin pole with a 50-foot boom and ¼-ton bucket has been used to excavate the pit. It is operated by a hand winch. Screens, hand shovels, and buckets of wash water are the only other equipment used. As near as can be determined, beryl has constituted less than 0.5 percent of the material excavated to the time of this examination."

*Update: During the spring of 2010, the property was sold to the State of CT and absorbed into the Meshomasic State Forest*

References

Barton, William R. and Carl E. Goldsmith. (1968): New England Beryllium Investigations. U. S. Bureau of Mines, Report of Investigations 7070.

Jarnot, Bruce. (1995): The Brack Prospect: A Decomposed Lithia Gem Pegmatite in Glastonbury, Connecticut. Rocks & Minerals: 70(2) (March/April 1995): 128.

Jarnot, Bruce. (1995): Connecticut Gems & Gem Minerals. Rocks & Minerals (Connecticut Issue): 70(6)(Nov.-Dec.): 378-382.

Weber, Marcelle H. and Earle C. Sullivan. (1995): Connecticut Mineral Locality Index. Rocks & Minerals (Connecticut Issue): 70(6)(Nov.-Dec.): 396-409.

Mineral List

Albite var: Cleavelandite Beryl var: Aquamarine var: Goshenite

Beryl var: Morganite Cassiterite Columbite Cookeite Elbaite

Kaolinite Lepidolite Microcline Microlite Group Muscovite

Quartz var: Smoky Quartz Spessartine Staurolite 'Tourmaline var: Rubellite'

20 entries listed. 13 valid minerals.