LIVE REPORT! Denver Mineral Shows 2019 - last updated 4 minutes ago. Click here to watch.
Log InRegister
Home PageAbout MindatThe Mindat ManualHistory of MindatCopyright StatusWho We AreContact UsAdvertise on Mindat
Donate to MindatCorporate SponsorshipSponsor a PageSponsored PagesMindat AdvertisersAdvertise on Mindat
Learning CenterWhat is a mineral?The most common minerals on earthInformation for EducatorsMindat ArticlesThe ElementsBooks & Magazines
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralRandom LocalitySearch 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
Mining CompaniesStatisticsUsersMineral MuseumsMineral Shows & EventsThe Mindat DirectoryDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day GalleryMineral Photography

Great Hill Pond Brook pegmatite, Cobalt, East Hampton (Chatham), Middlesex Co., Connecticut, USA

This page is currently not sponsored. Click here to sponsor this page.
Latitude & Longitude (WGS84): 41° 34' 15'' North , 72° 33' 34'' West
Latitude & Longitude (decimal): 41.57083,-72.55944

A granite pegmatite exposed at the waterfall on Great Hill Pond Brook about 350 meters downstream of the pond. Prospected before 1927 based on its first mention in the literature by Rice and Foye (1927):

The path which we follow up the valley is in places indistinct, and, when the brook is full, as is usual in the springtime, requires some wading. At the head of the valley, we find that the brook comes down in a cascade over a ledge of pegmatite. Our path has followed mostly the right bank of the brook (our left, as we face upstream). The ledge of pegmatite extends some distance to our right from the situation of the cascade. We see at once that considerable work has been done in quarrying pegmatite. The quarry, however, was soon abandoned. Very likely one reason for its abandonment was that the pegmatite there contains large quantities of black tourmaline and black mica; since the presence of dark, iron-holding minerals in large quantity diminishes the value of the rock for the purposes to which it is applied. We cross the brook (an easy task in late summer, but in spring and early summer it requires some wading), and ascend by a road or path a short distance to the right of the exposure of pegmatite. The large masses of black tourmaline are very conspicuous, and other somewhat interesting minerals may be seen. Near the top of the exposure of pegmatite, we find a path leading east, passing a couple of shanties which were used while the quarry was being worked and one of which is badly ruined.

Schooner (1958 and/or 1961) mentions well-formed black tourmaline and "spessartine" (likely almnadine-spessartine mix) from here. In 1961 he describes similar garnet from the Nathan Hall quarry on Clark Hill a mile or so to the NE Schooner later incorrectly calls the Nathan Hall Quarry the "Hale Quarry" in his unpublished central Connecticut mineralogy. This occurs in the text for "spessartine" localities right after he mentions garnet from the Great Hill Pond Brook falls pegmatite. This may have led to confusion by Hiller (1971) who marks this prospect on a map of the Cobalt area localities as "Nathan Hale [sic] Quarry". While it may just be an error by Hiller (the source he used for the name is not recorded), it is possible that Nathan Hall, who's family owned much land in the area in the 19th century, prospected this pegmatite as well, given that Foye in 1922 stated that the Nathan Hall Quarry was long abandoned. Nathan Hall had quarry properties in Haddam Neck also. However, so far the exact history of this little prospect is unknown.

The brook is the border between Portland (west) and the Cobalt section of East Hampton (east), but because the pegmatite extends mostly east of the brook, it is listed here as in the latter town. The site is now residential private property.

Mineral List

5 valid minerals.

Rock Types Recorded

Note: this is a very new system on and data is currently VERY limited. Please bear with us while we work towards adding this information!

Select Rock List Type

Alphabetical List Tree Diagram

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

Late Ordovician - Middle Ordovician
443.8 - 470 Ma
Collins Hill Formation

Age: Ordovician (443.8 - 470 Ma)

Stratigraphic Name: Collins Hill Formation

Description: ( = Partridge Formation of New Hampshire) - Gray, rusty-weathering, medium- to coarse-grained, poorly layered schist, composed of quartz, oligoclase, muscovite, biotite, and garnet, and commonly staurolite, kyanite, or sillimanite, generally graphitic, interlayered with fine-grained two-mica gneiss, especially to the west, and with calc-silicate and amphibolite layers, also rare quartz-spessartine (coticule) layers.

Comments: Part of Eastern Uplands; Iapetus (Oceanic) Terrane - Bronson Hill Anticlinorium; Brimfield Schist and equivalent formations (includes Collins Hill Formation) (Upper? and Middle Ordovician).

Lithology: Major:{schist}, Minor:{gneiss}, Incidental:{amphibolite, calc silicate rock}

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.


Rice, William North and Wilbur Garland Foye. (1927), Guide to the Geology of Middletown, Connecticut, and Vicinity. State Geological and Natural History Survey Bulletin 41.

Schooner, Richard. (1958), The Mineralogy of the Portland-East Hampton-Middletown-Haddam Area in Connecticut (With a few notes on Glastonbury and Marlborough). Published by Richard Schooner; Ralph Lieser of Pappy’s Beryl Shop, East Hampton; and Howard Pate of Fluorescent House, Branford, Connecticut.

Stugard, Frederick, Jr. (1958), Pegmatites of the Middletown Area, Connecticut. USGS Bulletin 1042-Q.

Jones, Robert W. (1960), Luminescent Minerals of Connecticut, a Guide to Their Properties and Locations.

Schooner, Richard. (1961), The Mineralogy of Connecticut. Fluorescent House, Branford, Connecticut.

Hiller, John, Jr. (1971), Connecticut Mines and Minerals. Privately published: 52.

Schooner, Richard. (circa 1980s), Untitled manuscript on central Connecticut mineralogy.

Mineral and/or Locality is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization. Public Relations by Blytheweigh.
Copyright © and the Hudson Institute of Mineralogy 1993-2019, except where stated. Most political location boundaries are © OpenStreetMap contributors. relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: September 15, 2019 17:34:09 Page generated: October 15, 2017 06:06:06
Go to top of page