Great Hill Pond Brook pegmatite, Cobalt, East Hampton (Chatham), Middlesex County, Connecticut, USAi
| Regional Level Types | |
|---|---|
| Great Hill Pond Brook pegmatite | Pegmatite |
| Cobalt | Prospect |
| East Hampton (Chatham) | Quarry |
| Middlesex County | County |
| Connecticut | State |
| USA | Country |
This page is currently not sponsored. Click here to sponsor this page.
Latitude & Longitude (WGS84):
41° 34' 14'' North , 72° 33' 33'' West
Latitude & Longitude (decimal):
Type:
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| East Hampton | 2,691 (2017) | 4.8km |
| Lake Pocotopaug | 3,436 (2017) | 5.1km |
| Portland | 5,862 (2017) | 6.8km |
| Cromwell | 13,750 (2017) | 7.6km |
| Middletown | 46,756 (2017) | 7.6km |
Nearest Clubs:
Local clubs are the best way to get access to collecting localities
Local clubs are the best way to get access to collecting localities
| Club | Location | Distance |
|---|---|---|
| Lapidary and Mineral Society of Central Connecticut | Meriden, Connecticut | 21km |
| Bristol Gem & Mineral Club | Bristol, Connecticut | 34km |
| New Haven Mineral Club | New Haven, Connecticut | 42km |
Mindat Locality ID:
253771
Long-form identifier:
mindat:1:2:253771:2
GUID (UUID V4):
a96ace2c-73bc-4a27-b8c8-7520aac1b329
A granite pegmatite exposed at the waterfall on Great Hill Pond Brook about 350 meters downstream of the pond. Technically it is in the town of Portland, but has is right near the line and has been historically referred to as being in Cobalt. 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 www.mindat.org/loc-29586.html. 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.
Select Mineral List Type
Standard Detailed Gallery Strunz Chemical ElementsMineral List
6 valid minerals.
Rock Types Recorded
Note: data is currently VERY limited. Please bear with us while we work towards adding this information!
Select Rock List Type
Alphabetical List Tree DiagramDetailed Mineral List:
| ⓘ Albite Formula: Na(AlSi3O8) Description: Pegmatite matrix. |
| ✪ 'Almandine-Spessartine Series' Habit: trapezohedral Colour: dark maroon with black coating Description: Crystals to 4 inches. Referred to by Schooner as spessartine, but most likely impure almandine based on XRF analyses of many other district pegmatitic garnets. References: |
| ⓘ Annite Formula: KFe2+3(AlSi3O10)(OH)2 Colour: black |
| ⓘ Microcline Formula: K(AlSi3O8) Description: Pegmatite matrix. |
| ⓘ Muscovite Formula: KAl2(AlSi3O10)(OH)2 References: |
| ⓘ Quartz Formula: SiO2 Description: Pegmatite matrix. |
| ⓘ Quartz var. Rose Quartz ? Formula: SiO2 Habit: massive Colour: pink Description: On display at the Joe Webb Peoples museum, attributed to "Cobalt", but as this locality is the only significant pegmatite in the village, it is the likely source. |
| ✪ Schorl Formula: NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH) Habit: prismatic with rhombohedral terminations Colour: black Description: The quarry below the waterfall at the lower end of Great Hill Lake in Portland, downstream from the dam, was a source of excellent large crystals, with sharp faces (Schooner, 1961). References: |
Gallery:
List of minerals arranged by Strunz 10th Edition classification
| Group 4 - Oxides and Hydroxides | |||
|---|---|---|---|
| ⓘ | Quartz | 4.DA.05 | SiO2 |
| ⓘ | var. Rose Quartz ? | 4.DA.05 | SiO2 |
| Group 9 - Silicates | |||
| ⓘ | Schorl | 9.CK.05 | NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH) |
| ⓘ | Muscovite | 9.EC.15 | KAl2(AlSi3O10)(OH)2 |
| ⓘ | Annite | 9.EC.20 | KFe2+3(AlSi3O10)(OH)2 |
| ⓘ | Microcline | 9.FA.30 | K(AlSi3O8) |
| ⓘ | Albite | 9.FA.35 | Na(AlSi3O8) |
| Unclassified | |||
| ⓘ | 'Almandine-Spessartine Series' | - | |
List of minerals for each chemical element
| H | Hydrogen | |
|---|---|---|
| H | ⓘ Annite | KFe32+(AlSi3O10)(OH)2 |
| H | ⓘ Muscovite | KAl2(AlSi3O10)(OH)2 |
| H | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| B | Boron | |
| B | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| O | Oxygen | |
| O | ⓘ Albite | Na(AlSi3O8) |
| O | ⓘ Annite | KFe32+(AlSi3O10)(OH)2 |
| O | ⓘ Microcline | K(AlSi3O8) |
| O | ⓘ Muscovite | KAl2(AlSi3O10)(OH)2 |
| O | ⓘ Quartz | SiO2 |
| O | ⓘ Quartz var. Rose Quartz | SiO2 |
| O | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| Na | Sodium | |
| Na | ⓘ Albite | Na(AlSi3O8) |
| Na | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| Al | Aluminium | |
| Al | ⓘ Albite | Na(AlSi3O8) |
| Al | ⓘ Annite | KFe32+(AlSi3O10)(OH)2 |
| Al | ⓘ Microcline | K(AlSi3O8) |
| Al | ⓘ Muscovite | KAl2(AlSi3O10)(OH)2 |
| Al | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| Si | Silicon | |
| Si | ⓘ Albite | Na(AlSi3O8) |
| Si | ⓘ Annite | KFe32+(AlSi3O10)(OH)2 |
| Si | ⓘ Microcline | K(AlSi3O8) |
| Si | ⓘ Muscovite | KAl2(AlSi3O10)(OH)2 |
| Si | ⓘ Quartz | SiO2 |
| Si | ⓘ Quartz var. Rose Quartz | SiO2 |
| Si | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| K | Potassium | |
| K | ⓘ Annite | KFe32+(AlSi3O10)(OH)2 |
| K | ⓘ Microcline | K(AlSi3O8) |
| K | ⓘ Muscovite | KAl2(AlSi3O10)(OH)2 |
| Fe | Iron | |
| Fe | ⓘ Annite | KFe32+(AlSi3O10)(OH)2 |
| Fe | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
Other Regions, Features and Areas containing this locality
North America PlateTectonic Plate
- Ganderia DomainDomain
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
