Help|Log In|Register|
Home PageMindat NewsThe Mindat ManualHistory of MindatCopyright StatusManagement TeamContact UsAdvertise on Mindat
Donate to MindatSponsor a PageSponsored PagesTop Available PagesMindat AdvertisersAdvertise on Mindat
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralSearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
StatisticsThe ElementsMember ListBooks & MagazinesMineral Shows & EventsThe Mindat DirectoryHow to Link to MindatDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day Gallery

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

This page is currently not sponsored. Click here to sponsor this page.
Latitude & Longitude (WGS84): 41° 32' 33'' North , 73° 11' 47'' West
Latitude & Longitude (decimal): 41.5425, -73.1963888889

A trap rock quarry in basalt. Note that the O & G No. 2 Quarry 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 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

17 valid minerals.

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on

Early Jurassic
174.1 - 201.3 Ma
Holyoke Basalt

Age: Early Jurassic (174.1 - 201.3 Ma)

Stratigraphic Name: Holyoke Basalt

Description: Greenish-gray to black (weathers bright orange to brown), fine- to coarse-grained, grading from basalt near contacts to gabbro in the interior, composed of pyroxene and plagioclase with accessory opaques and locally olivine or devitrified glass.

Comments: Part of Central Lowlands; Newark Terrane - Hartford and Pomperaug Mesozoic Basins. Part of Newark Supergroup (Upper Triassic and Lower Jurassic). Part of Meriden Formation of Krynine (1950) (Lower Jurassic); CT005.

Lithology: Major:{basalt,gabbro}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Data and map coding provided by, used under Creative Commons Attribution 4.0 License

This page contains all mineral locality references listed on 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 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.


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.

Mineral and/or Locality is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization.
Copyright © and the Hudson Institute of Mineralogy 1993-2017, except where stated. relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: October 19, 2017 22:56:33 Page generated: October 5, 2017 12:39:33
Go to top of page