Latitude: 41°27'23"N
Longitude: 72°31'40"W
The Route 9 divided, 4-lane expressway cuts diagonally through the metamorphic rocks of south-central Connecticut. In central Haddam, where Route 9 trends NW-SE, Interchange 8 (formerly 7) connects it with Beaver Meadow Road, which crosses it at nearly a right angle. This interchange was opened in 1969, the reference coordinates for its center are given below.
Extensive and deep roadcuts along both sides of the divided highway, the 4 on and off-ramps, and nearby Hubbard Road have exposed rock units of the Middletown Formation, a metamorphic sequence consisting mostly of amphibolite, orthoamphibole gneiss, and biotite gneiss. Lundgren (1979) provides a detailed map and description of the rock units and their mineralogy at this interchange. Most of the minerals mentioned are rock-forming grains, but he notes one distinctive unit, “A gneiss in which gedrite occurs in well aligned prisms and in conspicuous rosettes of prisms. This unit also contains cordierite. It is well displayed in the cut on Hubbard Road at Beaver Meadow Road, the entrance to the northbound lane of Route 9, and in the exit from the southbound lane of Route 9 at Beaver Meadow Road”.
Bannerman, Quarrier, and Schooner (1968) gave the following descriptions of minerals at the roadcuts:
North side of Beaver Meadow Road. The eastern side of the eastern most road cut. This is actually the newly blasted intersection of Hubbard Road and Beaver Meadow Road. Several small pegmatite lenses have intruded the gneiss in this cut and they contain small pockets of clear blue cordierite. While the blasting was under way last year some museum sized specimens of this mineral were recovered. Cordierite also occurs in lesser amounts in the surrounding gneiss.
North of Beaver Meadow Road. The western side of the cut of the north bound lane of Route 9. This cut is mostly in the Middletown Formation. Extremely coarse prisms of green-brown anthophyllite can be found on the surfaces between the layers of dark and light colored gneiss. This mineral is characteristic of the Middletown Formation in this area.
North of Beaver Meadow Road, on the east side of the cut for the south bound lane of Route 9. A pegmatite at the south end of this cut contains large well developed crystals of magnetite, some nearly an inch across.
South side of Beaver Meadow Road, on the west side of the south end of the southbound entrance ramp for Route 9. The small pegmatite body that is perched on the side of the hill has produced a number of interesting minerals including albite, bismuthinite, monazite, molybdenite, tourmaline and beryl.
Apparently, the later, more technical work by Lundgren (1979) identified the anthophyllite above as gedrite.
Hiller (1971) also noted bavenite at the “small pegmatite body” described above. This bavenite was described by Henderson (1970), which was "found in or close to hexagonal cavities after beryl or cavities still partially filled by corroded beryl crystals. Only small amounts of unaltered beryl were found." He noted one "single superb specimen of bavenite was found consisting of crystals so large that they have the pale apple green color of prehnite. The crystals comprise five fans on albite with black tourmaline. Each crystal is about 4 mm square by 0.2 mm thick".
Anecdotal information from mineral collectors describes a now lost location between this pegmatite and Beaver Meadow Road that produced sharp edged, doubly-terminated black tourmaline crystals from a chlorite schist.
An extensive blasted rock dump is present up to 0.5 km NNW of the interchange, in the area between Route 9 and Hubbard Road. Some of the minerals described have been found there as well, particularly large boulders of the gray, gedrite prism-bearing gneiss. This area was developed into residential lots circa 2007.
References
- Bannerman, Harold M., Sidney S. Quarrier, and Richard Schooner. (1968): MINERAL DEPOSITS OF THE CENTRAL CONNECTICUT PEGMATITE DISTRICT in Guidebook for Fieldtrips in Connecticut. State Geological and Natural History Survey of Connecticut. Guidebook No. 2, Trip F-6.
- Henderson, William, A., Jr. (1970): BAVENITE FROM CONNECTICUT. Mineralogical Record, volume 1, no. 2.
- Hiller, John Jr. (1971): CONNECTICUT MINES AND MINERALS. Privately published.
- Lundgren, Lawrence, Jr. (1979): THE BEDROCK GEOLOGY OF THE HADDAM QUADRANGLE. State Geological and Natural History Survey of Connecticut. Quadrangle Report No. 37, pages 9-13.
- Weber, Marcelle H. and Earle C. Sullivan. (November/December 1995) CONNECTICUT MINERAL LOCALITY INDEX. Rocks & Minerals (Connecticut Issue), Volume 70, No. 6, p. 403.
Mineral List
23 entries listed. 17 valid minerals.
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