|Latitude & Longitude (WGS84):||41° 52' 19'' North , 72° 16' 24'' West|
|Latitude & Longitude (decimal):||41.87222,-72.27361|
|Köppen climate type:||Dfb : Warm-summer humid continental climate|
Most famous for its Tessin habit and sceptered quartz crystals, plus assemblage of magnesite, almandine, pyrite, tourmaline, and free-standing kyanite crystals. As described by Ague (1995), the host rock is a granulite facies mafic gneiss (metagabbro) consisting of anorthite (An70-80), clinopyroxene, orthopyroxene and biotite with accessory quartz, and retrograde magnesio-hornblende and cummingtonite. Hydrothermal vein minerals formed in open Alpine-type fractures that cross-cut the foliation of the bedrock when it was under amphibolite facies conditions - about 15-30 km deep and 500-550 degrees C. The most common assemblage is quartz-almandine-kyanite-magnesite-biotite-albite (An20-40)-ankerite-muscovite. Less common is quartz-almandine-magnesio-hornblende-magnesite-albite (An20-40)-ankerite-biotite. Also in the veins are accessory staurolite, fluorapatite, tourmaline, zircon, ilmenite, pyrrhotite and chalcopyrite crystals (and rutile not mentioned by Ague). Calcite and pyrite formed under lower P-T conditions much later. Many minerals are coated with a dull gray-green layer of very fine-grained, retrograde sericite/chlorite/clay.
This is an operating quarry and collecting is not allowed without permission, which in recent years is rarely given.
21 valid minerals.
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
|Paleozoic sedimentary and volcanic rocks|
Age: Paleozoic (358.9 - 443.8 Ma)
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. 
|Ordovician - Cambrian|
443.8 - 541 Ma
|Gneiss (metavolcanic) member [of Brimfield Schist]|
Age: Paleozoic (443.8 - 541 Ma)
Stratigraphic Name: Brimfield Schist
Description: Medium-gray, medium-grained, layered gneiss and schist, composed of oligoclase, quartz, and biotite; some gneiss and most schist layers contain garnet and sillimanite; some gneiss layers contain garnet, hornblende or pyroxene or grade into amphibolite or calc-silicate rock. Probably includes metavolcanic rocks.
Comments: Part of Eastern Uplands; Iapetus (Oceanic) Terrane - Merrimack Synclinorium; Brimfield Schist and equivalent formations (includes Tatnic Hill Formation) (Upper? and Middle Ordovician). The age of the Brimfield Group in this area is Cambrian(?) based on the intrusion of 440 my Hedgehog Hill gneiss in the top of the Hamilton Reservoir Formation in the upper part of the Brimfield, although the top of the Brimfield may be Ordovician or older Paleozoic (Pease, 1989) per CT013.
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.