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O & G Southbury Quarry (Silliman Quarry; O & G No. 2 Quarry), Southbury, New Haven Co., Connecticut, USA

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Latitude & Longitude (WGS84): 41° 30' 50'' North , 73° 12' 58'' West
Latitude & Longitude (decimal): 41.5138888889, -73.2161111111


Note, the entrance road to this quarry is on State Route 67 in Southbury; however, the quarry starts about 0.5 mile north of the entrance road and the vast majority of it is mostly in Woodbury. Because O & G operates another quarry farther north in Woodbury (O & G No. 1 or the "Woodbury" Quarry), this locality has almost universally been referred to as the "Southbury" Quarry to differentiate it, even though it too is technically in Woodbury. It has been referred to as the Silliman Quarry, but that name initially referred to an earlier sand pit a little to the south. However, Brunet (1977) states that the Silliman family, descended from Yale mineralogist Benjamin Silliman, owned the trap rock quarry, too, at that time.

Collecting field trips were kindly allowed until about 2000 when someone violated the rules, closing the site for all but a few with special permission.

Well known Connecticut locality for prehnite. Three varieties are found - the standard green, rare yellow prehnite, and the extremely rare white prehnite that is almost completely free of iron impurities. Particularly noteworthy are prehnite floater specimens called "hearts". According to Garabedian (1998) these formed via a 5-step process:

1. Chalcedony precipitation on vesicle walls as "fortification" agate.
2. Chalcedony (or partial white, fine-grained, chalky quartz replacement of initial chalcedony) is replaced by fine-grained, white, granular datolite.
3. Prehnite encrusts and/or partly replaces the datolite replacement.
4. Datolite dissolves, leaving a floater of prehnite with large crystals on the inside (small ones may be present on the outside where the datolite was partly replaced by initial prehnite).
5. More prehnite forms on the outside of the prehnite floater, resulting in aggregates with large prehnite crystals on both sides.

Examples of all the intermediate steps can be found in the vesicles.

Other noteworthy pseudomorphing described by Garabedian (1998) include:

- Pumpellyite replacement of chalcedony.
- Tabular anhydrite crystals epimorphed by chalcedony, quartz, a trapezohedral zeolite, or pumpellyite; the anhydrite later dissolves.
- Prehnite or pumpellyite encrust a trapezohedral zeolite (wairakite or analcime), which later dissolves, and more prehnite or pumpellyite partly or completely fill in the void.
- Sequential "water level" vesicle fillings by thin layers of ferroan calcite that are later epimorphed by quartz, chalcedony, datolite or pumpellyite.

Late forming minerals include pyrite, gemmy green sphalerite crystals to about 6mm, calcite as dogteeth or various rhombohedra, apophyllite, babingtonite, julgodite/pumpellyite, drusy quartz (some amethystine) and zeolites.

Faulting created brecciated zones and cross-cutting veins filled with coarse-grained, columnar, parallel-growth calcite the grew from opposite walls and commonly stained with red, earthy hematite. These veins can reach around 1 meter thick.

Mineral List


23 valid minerals.

This page contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.

References

Silliman, Benjamin. (1819), New localities of agate, chalcedony, chabazite, stilbite, analcime, prehnite, etc. American Journal of Science: 1: 134-135.

Brunet, William. (1977), Mineral Collecting in Woodbury-Southbury, Connecticut. Rocks and Minerals: 52(4): 182-183.

Weber, Marcelle H. and Earle C. Sullivan. (1995), Connecticut Mineral Locality Index. Rocks & Minerals (Connecticut Issue): 70(6): 407.

Garabedian, James A. (1998), Secondary Mineralization of Half-Moon Vesicles in the Mesozoic Basalt of the O&G#2 Quarry, Woodbury, Connecticut. University of Connecticut Master of Science Thesis.

Vajdak, Josef. (1998): New Mineral Finds in the Second Half of 1997, News from Josef Vajdak of Pequa Rare Minerals and Metals. Mineral News: 14(1): 4.

Moore, Thomas. (2007): What's New in Minerals. Mineralogical Record: 38(3): 214.


External Links

www.johnbetts-fineminerals.com/jhbnyc/mineralmuseum

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