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O & G Woodbury Quarry (Orenaug Quarry; O & G No. 1 Quarry), Orenaug Hills, Woodbury, Litchfield Co., Connecticut, USA
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Prehnite
O & G Woodbury Quarry, Orenaug Hills, Woodbury, Litchfield Co., Connecticut, USA

Photo: 2001 John H. Betts
Latitude: 41°32'33"N
Longitude: 73°11'47"W
 
 
A trap rock quarry in basalt. Note that the O & G No. 2 Quarry http://www.mindat.org/loc-5370.html is also mostly situated in Woodbury, but because the entrance to the quarry is further south on Route 67 in Southbury, the No. 2 quarry is nearly universally called the Southbury Quarry. Januzzi (1976) refers to the Woodbury Quarry, but his description of the locality as off of Route 67 and synonymous with the Silliman Quarry indicates that he is actually discussing finds from the Southbury (No. 2) Quarry. Thus, minerals listed from Januzzi (1976) should be listed in the mindat page for the O & G Southbury or No. 2 quarry. In general the operations at the No. 1 quarry are older than at No. 2, with No. 1 being largely idle since the late 1990s.

There is, however, much similarity between the mineralogy of both quarries as they are in the same basalt formation only a few miles apart. As such, the descriptions below of the paragenesis and species for O & G No. 2 Quarry http://www.mindat.org/loc-5370.html is also valid for this quarry:

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 rhombs, apophyllite, babingtonite, julgodite, drusy quartz and zeolites.

Mineral List

Analcime
'Apophyllite'
Aragonite
Babingtonite
Baryte
Calcite
'Chabazite'
Chalcopyrite
'Chlorite Group'
Datolite
Epidote
Fluorite
Galena
Hematite
'Heulandite'
Laumontite
'Limonite'
Natrolite
Prehnite
'Pumpellyite'
Pyrite
Quartz
var: Agate
var: Amethyst
var: Chalcedony
var: Smoky Quartz
'Stilbite'


27 entries listed. 16 valid minerals.

The above list 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

Zodac, Peter. (1938), Prehnite. Rocks & Minerals: 13(5): 131.

Januzzi, Ronald E. (1976), Mineral Localities of Connecticut and Southeastern New York State. The Mineralogical Press, Danbury, Connecticut.

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

Tschernich, Rudy. (1992): Zeolites of the World, 65.

Weber, Marcelle H. and Earle C. Sullivan. (1995), Connecticut Mineral Locality Index. Rocks & Minerals (Connecticut Issue), 70(6): 401.

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.

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