Latitude: 41°37'31"N
Longitude: 72°34'47"W
The four Case quarries lie in the town of Portland, 4.5 miles N. 39° E. of the center of Portland village. Cameron et al (1954) reported that the property was owned by Myron N. Case, Rose Hill, Portland. Although known as 'beryl prospects', actual mining was for feldspar and mica. From 1933 to 1935, the Worth Spar Co., Inc. quarried the nos. 1, 2 & 3 pegmatites (located within 500 feet of one another) for feldspar, and in 1939 Frank Bajorek of Portland mined the no. 1 pegmatite for feldspar. Then the Worth Spar Co. prospected the no. 2 pegmatite for sheet mica in August and October 1942. Exploratory drilling to estimate beryl resources was done by the U. S. Bureau of Mines (Boos, Maillot & Mosier, 1949), but commercial beryl production was not recommended, beryl removal being limited to subsequent decades of specimen collecting.
During the fall of 1983 a fourth pegmatite was discovered in the middle of the other three (Cross, 1987), amazingly missed by all the earlier drilling. This pegmatite was very rich in beryl, and was worked by local mineral collectors for beryl crystals. It probably yielded the best specimens.
All four pegmatites are relatively small dikes (roughly 2 to 8 m wide) cross-cutting the Glastonbury Gneiss and are zoned to varying degrees. They generally have a thin border/wall zone a few to several cm thick consisting of fine-grained granular quartz, albite, and microcline perthite, with accessory muscovite, beryl, schorl, almandine, and columbite-tantalite. This zone grades into a coarse-grained intermediate zone 0.3 to 2 m thick consisting of microcline perthite and quartz, with subordinate albite, beryl and muscovite (progressively coarser toward the center of the pegmatite), and either a pure quartz core zone or irregular quartz bodies. Microcline crystals in the intermediate zone are euhedral against the quartz.
Beryl occurs in the border/wall zones as scattered, subparallel crystals that tend to be oriented with their c axes roughly perpendicular to the contact. Their diameters at the contact are only a few mm, with increasing diameter toward the core, resulting in tapered, subhedral crystals around 5 to 10 cm or more long. Cameron et al (1954) reports beryl crystals in the no. 2 pegmatite intermediate zone 22 cm in diameter and 25 mm long. Similar beryls were found in the no. 4 pegmatite, with flat, euhedral terminations in the quartz core, where dozens of beryl molds can still be seen in the quartz. Cross (1987) reports individual crystals weighing over 22 kilograms. The beryl crystals are colored white, yellow, pale to deep green, and pale to deep blue, with the blue to green colors being typical. The crystals are frozen in matrix, but a few pocket crystals are known.
Other pegmatite minerals, both common and rare, are reported in the references listed below. Particularly noteworthy are the bismuth mineral suite, small but usually excellent columbite-(Fe) crystals to 5 cm, sub to euhedral red-brown monazite-(Ce) crystals around 1 cm or so, and the very rare minerals liandratite and possibly petscheckite. These last two species are based on unpublished X-ray diffraction testing by Fred Davis.
The bismuth minerals occur together, being produced by successive weathering of primary bismuthinite, which occurs as lead-grey, metallic sectile masses. The bismite occurs here as tiny, light yellow or green massive fragments that are scaly or earthy. Bismutite reportedly is bright green and is found in thin scaly masses with a vitreous or pearly luster. Goethite is usually associated with them. Huff, Huff, & Vajdak (1996) report that pyrite is associated with the bismuthinite (apparently weathering into the goethite) and based on XRD and microprobe analyses, the bright green mineral reported as bismutite is bismutoferrite.
Collecting is allowed via permit issued by the Connecticut DEP to educational organizations (schools, mineral clubs, etc.). See link below.
Mineral List
49 entries listed. 33 valid minerals. 3 erroneous literature entries.
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References
- Boos, M. F., E. E. Maillot and McHenry Mosier. (March 1949) INVESTIGATION OF PORTLAND BERYL-MICA DISTRICT, MIDDLESEX COUNTY, CONN. U. S. Bureau of Mines Report of Investigation 4425.
- Cameron, Eugene N. and others. (1954) PEGMATITE INVESTIGATIONS 1942-45 NEW ENGLAND. U.S. Geological Survey, Professional Paper 255.
- Schooner, Richard. (1958) THE MINERALOGY OF THE PORTLAND-EAST HAMPTON-MIDDLETOWN-HADDAM AREA IN CONNECTICUT (With a few notes on Glastonbury and Marlborough).
- Stugard, Frederick, Jr. (1958) PEGMATITES OF THE MIDDLETOWN AREA, CONNECTICUT. USGS Bulletin 1042-Q.
- Jones, Robert W. (1960) LUMINESCENT MINERALS OF CONNECTICUT, A GUIDE TO THEIR PROPERTIES AND LOCATIONS.
- Schooner, Richard. (1961) THE MINERALOGY OF CONNECTICUT.
- Ryerson, Kathleen. (1972) ROCK HOUND'S GUIDE TO CONNECTICUT.
- Webster, Bud. (1978) MINERAL COLLECTOR’S FIELD GUIDE CONNECTICUT.
- Albini, Anthony J. (1979) SELECTED PEGMATITE QUARRIES OF THE CENTRAL CONNECTICUT REGION. Masters thesis.
- Webster, Bud and Bill Shelton. (1979) MINERAL COLLECTOR’S FIELD GUIDE THE NORTHEAST.
- Cross, L. M. (March-April 1987) A NEW OCCURRENCE OF BERYL AT CASE QUARRIES, PORTLAND, CONNECTICUT. Rocks & Minerals, Volume 62, No. 2, Pages 116-7.
- Weber, Marcelle H. and Earle C. Sullivan. (November/December 1995) CONNECTICUT MINERAL LOCALITY INDEX. Rocks & Minerals (Connecticut Issue), Volume 70, No. 6, p. 403.
- Huff, R. C., R. G. Huff, J. Vajdak. (May-June 1996) AN OCCURRENCE OF BISMUTOFERRITE IN PORTLAND, CONNECTICUT. Rocks & Minerals, Volume 71, No. 3, p. 197.
- Davis, Fred E. (June-July 2000) JUNE 17TH FIELD TRIP: CASE PROSPECTS. Triassic Valley Bulletin, New Haven Mineral Club.
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