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Garnet prospect, Middle Haddam, East Hampton (Chatham), Middlesex Co., Connecticut, USAi
Regional Level Types
Garnet prospectProspect
Middle Haddam- not defined -
East Hampton (Chatham)- not defined -
Middlesex Co.County

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Latitude & Longitude (WGS84): 41° 33' 8'' North , 72° 32' 53'' West
Latitude & Longitude (decimal): 41.55222,-72.54806
GeoHash:G#: drkkmhk55
Locality type:Prospect
Köppen climate type:Dfa : Hot-summer humid continental climate

This is one of these small places that seems to get more mention than it warrants.

The first one is by Taylor (1824):

Garnets, in mica-slate, at Middle Haddam.
They are found about eighty rods east of the Landing. They occur in vast abundance, and are from one to two inches diameter.

Schairer (1931):

There is an old garnet mine located on the side of the hill just north of an old road running east from Middle Haddam.

Schooner (1958) mentions it briefly in a few places:

A brown mineral, closely resembling anthophyllite, is abundant in gneiss at the old garnet mine in Middle Haddam...

Large reddish [staurolite] crystals, unfortunately rough and of very poor quality, can be found in the ledges near the old garnet mine in Middle Haddam....

Last worked in 19th Century (?).

A resident and collector has described it as beside the road and not much more than a small prospect pit. Taylor's directions place it in a depression on the south side of Schoolhouse Road with no rock now exposed. Area is residential private property. The garnet is almost certainly the species almandine, as that is by far the most common schist-hosted garnet in Connecticut.

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Mineral List

3 valid minerals.

Detailed Mineral List:

Formula: Fe2+3Al2(SiO4)3
Description: Not tested, but species probably almandine, as most schist-hosted garnets in Connecticut have proven to be. Crystals to 1-2 inches.
Reference: Taylor, Steuben. (1824), Miscellaneous localities of minerals. American Journal of Science: s. 1, 7: 253-4.; Schairer, J. F. (1931), The Minerals of Connecticut. State Geological and Natural History Survey Bulletin 51.
Formula: ☐{Mg2}{Mg5}(Si8O22)(OH)2
Description: Could be the brown mineral Schooner (1958) says looks like anthophyllite.
Reference: Harvard Mineralogical Museum
Formula: Fe2+2Al9Si4O23(OH)
Colour: reddish
Reference: Schooner, Richard. (1958): The Mineralogy of the Portland-East Hampton-Middletown-Haddam Area in Connecticut (With a few notes on Glastonbury and Marlborough).

List of minerals arranged by Strunz 10th Edition classification

Group 9 - Silicates

List of minerals arranged by Dana 8th Edition classification

Group 51 - NESOSILICATES Insular SiO4 Groups Only
Insular SiO4 Groups Only with cations in [6] and >[6] coordination
Group 52 - NESOSILICATES Insular SiO4 Groups and O,OH,F,H2O
Insular SiO4 Groups and O, OH, F, and H2O with cations in [4] and >[4] coordination
Group 66 - INOSILICATES Double-Width,Unbranched Chains,(W=2)
Amphiboles - Mg-Fe-Mn-Li subgroup

List of minerals for each chemical element

H Cummingtonite☐{Mg2}{Mg5}(Si8O22)(OH)2
H StauroliteFe22+Al9Si4O23(OH)
O AlmandineFe32+Al2(SiO4)3
O Cummingtonite☐{Mg2}{Mg5}(Si8O22)(OH)2
O StauroliteFe22+Al9Si4O23(OH)
Mg Cummingtonite☐{Mg2}{Mg5}(Si8O22)(OH)2
Al AlmandineFe32+Al2(SiO4)3
Al StauroliteFe22+Al9Si4O23(OH)
Si AlmandineFe32+Al2(SiO4)3
Si Cummingtonite☐{Mg2}{Mg5}(Si8O22)(OH)2
Si StauroliteFe22+Al9Si4O23(OH)
Fe AlmandineFe32+Al2(SiO4)3
Fe StauroliteFe22+Al9Si4O23(OH)

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 Macrostrat.org

Devonian - Silurian
358.9 - 443.8 Ma

ID: 3186140
Paleozoic sedimentary and volcanic rocks

Age: Paleozoic (358.9 - 443.8 Ma)

Lithology: Mudstone-carbonate-sandstone-conglomerate

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Late Ordovician - Middle Ordovician
443.8 - 470 Ma

ID: 2771940
Metavolcanic member [of Collins Hill Formation]

Age: Ordovician (443.8 - 470 Ma)

Stratigraphic Name: Collins Hill Formation

Description: Ranges from mafic to felsic, from dark layered amphibolite and hornblende schist, locally with garnet or epidote, to light-gray (in places purplish), laminated gneiss, composed of quartz, oligoclase, and biotite, in which some layers contain garnet (generally manganiferous) and hornblende or cummingtonite.

Comments: Part of Eastern Uplands; Iapetus (Oceanic) Terrane - Bronson Hill Anticlinorium; Brimfield Schist and equivalent formations (includes Collins Hill Formation) (Upper? and Middle Ordovician). Original map source: Connecticut Geological and Natural History Survey, DEP, in cooperation with the U.S. Geological Survey, 2000, Bedrock Geology of Connecticut, shapefile, scale 1:50,000

Lithology: Major:{amphibolite,schist,gneiss}

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 Macrostrat.org, used under Creative Commons Attribution 4.0 License


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Year (asc) Year (desc) Author (A-Z) Author (Z-A)
Taylor, Steuben. (1824), Miscellaneous localities of minerals. American Journal of Science: s. 1, 7: 253-4.
Schairer, John F. (1931), Minerals of Connecticut. Connecticut Geological and Natural History Survey Bulletin 51.
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.

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