Spinelli prospect (Spinelli quarry), Glastonbury, Hartford County, Connecticut, USAi

Regional Level Types
Spinelli prospect (Spinelli quarry)	Prospect
Glastonbury	Town
Hartford County	County
Connecticut	State
USA	Country

The locality is frequently reported as being in the South or East Glastonbury sections of the town of Glastonbury, but it is basically located in East Glastonbury. The late Richard Schooner in his private publication (1980) said it was north of Buck's Corner in East Glastonbury. It is located on private property near homes and permission is needed to access the prospect, which is now closed.

It is 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 then 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 a shallow trench in the westernmost end of the pegmatite. Richard Schooner (1980) in his unpublished manuscript says that hundreds of pounds were marketed in the 1930s, however, this amount cannot be verified. 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).

With permission from the owner granted to Anthony J. Albini, specimen mining took place from April 2008 to June 2013. Recovery of additional samarskite from the trench worked in 1932-4 is described in Davis and Nicolescu (2011) and A. J. Albini, privately published (2013) and Albini & Moritz (2013). The samarskite and accompanying columbite-(Fe) occurs in a medium-grained microcline perthite-albite-quartz-muscovite zone at the west end of the pegmatite. The microcline and albite are typically stained brick red near the samarskite and columbite crystals by what appears to be hematite and have partially altered. Large monazite-(Ce) crystals have also been found in early 2012 by Anthony J. Albini and Raymond Meyers. Specimen recovery ended when no more gamma-ray scintillometer readings were obtained and the pegmatite dips too far under the adjacent gneiss for further work. Subsequently, the trench has been filled in and there is nothing further to see or collect. The owners kindly ask to be left in peace.

Accessory minerals magnetite and garnet occur scarcely at the eastern end of the pegmatite, where most of the feldspar prospecting took place. These dumps have been thoroughly checked with scintillometers and nothing radioactive was found.

Other Regions, Features and Areas containing this locality

References