A roughly 1.6 km square (1 mile square) sub-district of the greater Middletown Pegmatite District of Connecticut. This area is named for the prominent, white, once treeless pegmatite ridges visible in the highlands to the east of Middletown center. It is situated between the Hartford Mesozoic Basin to the west, the Maromas Granite Gneiss to the east, the Connecticut River to the north, and reservoir and state forest land to the south. Quarrying took place on 5 major north to northwest-trending pegmatite dikes or dike complexes, a large northeast-trending dike, and several smaller dikes. The area was active from about 1907 to 1993, producing 18 quarries with all the major quarries since flooded, filled, and/or built over.
With foresight Bastin (1910) briefly states:
"The White Rocks region is in general one of the most promising known to the writer for quarrying the best grades of feldspar...The situation is also favorable for cheap quarrying and shipment."
However, the area does not have good muscovite and so for decades could not compete with the quarries that received federal subsidies for this mineral. Most of the quarrying was done by The Feldspar Corp. after they took over the property in 1959 and leased additional land to the east. Unlike earlier pegmatite quarrying in Connecticut, by this time the feldspar was not sorted by laborious hand cobbing, but was crushed and sorted by chemical floatation. This allowed all of the pegmatite to be quarried and used, rather than just the zone of subhedral to euhedral microclines that grew against the quartz-rich core of internally zoned pegmatites. Quartz and ground mica were also produced. Consequently, as other quarries shut down following the end of mica and beryl subsidies that had made them economical, the White Rock district took off as the major pegmatite mining area of the state, profitably using mostly the large but poorly zoned pegmatites characteristic of the area.
This page summarizes all the minerals found in the pegmatites and host metamorphic rocks (Middletown and Collins Hill Formations) and the coordinates are for the approximate center of quarrying activity. Major sub-localities consist of the Riverside Quarry and White Rocks Quarry, situated on the so-called "Eastern Dike" of Watts and Rice & Foye; unnamed quarries on northeast trending dikes to the immediate south and east; and the large, 1000-meter-long quarry in the northeast-trending pegmatite in the extreme southeastern part of the district.
Because most of the quarries in this large area do not have names, they were referred to by collectors generally as the White Rocks Quarries, leading to confusion or lack of documentation of the exact origin of specific minerals or specimens. However, generally the mineralogy and texture of the pegmatites varies systematically across the district. The pegmatite in the Eastern Dike has the most complex texture, with well-defined internal zones including cleavelandite and quartz rich cores zones, and lithium and rare-element-rich chemistry that yielded many elbaite, lepidolite, beryl, microlite, columbite-(Fe) and uranium mineral specimens. To the immediate east and south, the dikes are still zoned but without the cleavelandite and have simpler chemistry, producing mainly only beryl, schorl, fluorapatite, and garnet as major accessory minerals. The large northeast-trending pegmatite at the extreme SE part of the area has the simplest texture with no zoning and the least abundant accessory mineralogy. However, it is crossed by quartz veins that include pyrite and at its NE end produced the best molybdenite crystals in Connecticut.
References
Rocks & Min.: 16: 279.
Altamura, Robert J. (1987): Bedrock Mines and Quarries of Connecticut. Connecticut Geological and Natural History Survey Natural Resources Atlas Series Map, 1:125,000 scale, with 41-p. booklet.
Bannerman, H. W., S. S. Quarrier, and R. Schooner. (1968): Mineral deposits of the central Connecticut pegmatite district, field trip F-6. In Guidebook for fieldtrips in Connecticut, 1-7. New England Intercollegiate Geological Conference, 60th annual meeting, Yale University, New Haven, Conn., 25-27 Oct. 1968.
Bastin, Edson S. (1910): Economic Geology of the Feldspar Deposits of the United States. U. S. Geol. Survey Bull. 420.
Cameron, E. N., D. M. Larrabee, A. N. McNair, J. J. Page, G. W. Stewart, and V. E. Shainin. (1954): Pegmatite investigations, 1942-45, in New England. U. S. Geological Survey Professional Paper 255.
Eaton and Rosenfeld. (1972): The Bedrock Geology of the Middle Haddam Quadrangle, Connecticut. U. S. Geol. Survey open file report.
Foye, W. G. (1922): Mineral Localities in the Vicinity of Middletown, Connecticut. American Mineralogist, v. 7.
Jones, Robert W. (1960): Luminescent Minerals of Connecticut. Fluorescent House.
London, David. (1985): Pegmatites of the Middletown District, Connecticut. State Geological and Natural History Survey of Connecticut, Department of Environmental Protection, Guidebook No. 6, Pp. 509-533.
Rice, W. N. and Foye, W. G. (1927): Guide to the Geology of Middletown, Connecticut and Vicinity. Connecticut Geol. & Nat. Hist. Survey Bull. No. 41.
Ryerson, Kathleen H. (1972): Rock Hound’s Guide to Connecticut. Pequot Handbook 3. Stonington: The Pequot Press.
Schairer, J. F. (1931): Minerals of Connecticut. State Geological and Natural History Survey, Bulletin No. 51.
Schooner, R. (1958): The mineralogy of the Portland-East Hampton-Middletown-Haddam area in Connecticut (with a few notes on Glastonbury and Marlborough). East Hampton and Branford, Conn.: Richard Schooner, Ralph Lieser, and Howard Pate.
Shepard, C. U. (1837): Report on the Geological Survey of Connecticut.
Stugard, Frederick. (1958): Pegmatites of the Middletown Area, Connecticut. U. S. Geological Survey Bulletin 1042-Q, U. S. Government Printing Office.
Watts, A. S. (1916): The Feldspars of the New England and North Appalachian States. U. S. Bureau of Mines Bull. 92.
Weber, Marcelle H. and Earle C. Sullivan. (November/December 1995) CONNECTICUT MINERAL LOCALITY INDEX. Rocks & Minerals (Connecticut Issue), Volume 70, No. 6, p. 403.
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