Latitude: 41°41'N
Longitude: 72°33'W
A small prospect in a granite pegmatite, about 40 meters long, 4.6 meters wide and 0.3 to 4.6 meters deep. It was first worked probably for feldspar in 1912. It was idle until 1932-4, when it was owned by Vito Spinelli, and was worked for the recovery of samarskite at the behest of Wilbur Foye of Wesleyan College. Foye was looking for a radioactive mineral in sufficient quantity for reliable radioisotope dating of pegmatites. Somewhere between "a few" and "fifty" pounds of samarskite was mined from the shallow westernmost end of the pegmatite. The radiogenic dates based on samarskite from Spinelli appear in the landmark paper by Nier et al. (1941) and in later studies in the 1950s and 1960s. Some of it was also sent to Harvard and the USGS for composition analysis and determination of atomic weights of radiogenic lead isotopes (such as for lead-206).
Recent recovery of additional samarskite is described in Davis and Nicolescu (2011). The samarskite and accompanying columbite-(Fe) occurs in a medium-grained microcline perthite-quartz-muscovite zone at the west end of the pegmatite. The microcline is typically brick red near the samarskite crystals and has partially altered. Very little samarskite or accessory minerals other than magnetite and garnet occur at the eastern end where most of the feldspar prospecting took place.
The locality has frequently been mis-attributed to the adjacent town South Glastonbury. It is located on private property near homes and permission is needed to access the prospect.
Mineral List
16 entries listed. 14 valid minerals. 2 erroneous literature entries.
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References
- Davis, Fred E. and Stefan Nicolescu. (2011): Samarskite Rediscovered at the Spinelli Prospect, Glastonbury, Connecticut. Bulletin of the Peabody Museum of Natural History 52(1):135-152.
- Palache, C., Berman, H. & Frondel, C. (1944), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume I: Elements, Sulfides, Sulfosalts, Oxides. John Wiley and Sons, Inc., New York. 7th edition, revised and enlarged, 834pp.: 799.
- 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).
- Schooner, Richard. (1961) THE MINERALOGY OF CONNECTICUT.
- Stugard, Frederick, Jr. (1958) PEGMATITES OF THE MIDDLETOWN AREA, CONNECTICUT. USGS Bulletin 1042-Q.
- Brookins, D.G., Fairbairn, H.W., Hurley, P.M., and Pinson, W.H. (1969): A Rb-Sr Geochronologic Study of the Pegmatites of the Middletown Area, Connecticut). Contributions to Mineralogy and Petrology 22, 157-168.
- Rocks & Minerals: 62: 413.
- Weber, Marcelle H. and Earle C. Sullivan. (November/December 1995) CONNECTICUT MINERAL LOCALITY INDEX. Rocks & Minerals (Connecticut Issue), Volume 70, No. 6, p. 403.
- Nier, A. O., R.W. Thompson and B.F. Murphey. (1941): The Isotopic Measurement of Geologic Time, III. Physical Review 60:112-116.
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