|Latitude & Longitude (WGS84):||41° 28' 38'' North , 72° 30' 45'' West|
|Latitude & Longitude (decimal):||41.47722,-72.51250|
|Köppen climate type:||Cfa : Humid subtropical climate|
Haddam is a town on the Connecticut River in Middlesex County that was settled by Europeans in the early 1700s. Besides Haddam center, the town includes other villages such as Haddam Neck (on the east side of the Connecticut River), Higganum, Tylerville, Shailerville, Ponset, Little City, and West Haddam. Haddam has a long history of quarrying, mineral discoveries and production. Its proximity to universities studying mineralogy (Wesleyan, Yale, Harvard, Amherst) and historic finds of chrysoberyl (world’s first in-situ crystals), fine epidote, columbite (first confirmed North American locality), heliodor, and of course the pocket elbaites and other minerals of the Gillette Quarry made it world famous.
Haddam displays rugged topography, with hills reaching over 600 feet above mean sea level. It is primarily underlain by Ordovician metamorphosed, plutonic, volcanic, and sedimentary rocks of the Bronson Hill volcanic arc terrane, with Ordovician to Silurian metasedimentary rocks of the Central Maine and Merrimack oceanic terranes under the town’s east. The oldest rocks are metaplutonic rocks of the northern Killingworth dome complex, found in a generally north-south belt under Higganum, Ponset, Little City, West Haddam and Hidden Lake areas. These are predominantly a gray orthogneisses; the Boulder Lake gneiss and the Pond Meadow gneiss. However, the Mississippian Hidden Lake gneiss occurs as a pluton in the core of the Killingworth dome.
Flanking the dome on the northwest and east are Ordovician metavolcanics of the Higganum Gneiss and Middletown Formation, consisting of amphibolites and mafic gneiss and schist with local areas rich in gedrite, anthophyllite, sillimanite, staurolite, kyanite, cordierite, garnet and tourmaline. Further out from the Middletown Formation are belts of the Collins Hill Formation, a mix of metasedimentary rocks consisting of schist, gneiss, amphibolite, calc-silicate, marble, and quartzite. The western belt of Collins Hill rocks crosses the extreme northwest corner of town, the eastern belt trends north-south from east of Rock Landing in Haddam Neck, through Haddam center and down to Turkey Hill Reservoir. It is most famous for hosting spectacular epidote crystals and other calc-silicate minerals found long ago in a solution cavity on the Hazen farm.
Immediately east of the eastern Collins Hill Formation is a belt of Monson Gneiss that was heavily quarried on Quarry Hill (above Injun Hollow Road in Haddam Neck), on Great Hill and on Long Hill. The first quarries, in Haddam Neck, were opened by Deacon Ezra Brainerd in 1762 and are among the first in the nation. The quarry on Great Hill opened in 1794. Easy access to the river and abundant rock allowed the Brainerd and Arnold families and others in Haddam to ship stone for building, paving, and fortifications all over the east coast for many decades. The favored rock on the west edge of the belt is a vertically foliated bluish-grey, biotite to hornblende gneiss that split easily into large slabs and was known locally as the “Allen vein” after its discoverer, quarryman David Allen. The exterior of the old county jail at the corner of state Route 154 and Jail Hill Road in Haddam center is faced with this stone.
The easternmost part of Haddam is underlain by calc-silicate gneiss and granofels of the Hebron Formation, part of the Merrimack oceanic terrane that is separated from the Bronson Hill terrane rocks to the west by the Cremation Hill Fault Zone. The fault is named for the hill in Haddam just south of Shailerville.
A minor but noteworthy rock is the Higganum Dike, an early Jurassic diabase intrusion that was a feeder dike for the Holyoke Basalt in the nearby Hartford Mesozoic Basin. The dike extends from nearly Long Island Sound, cuts diagonally northeast through Haddam, and continues well into northern New England. It is associated with Mesozoic brittle faulting that affected all of Connecticut. Where such faulting brecciated quartzite on the west side of Long Hill, abundant and large (over 25 cm) quartz crystals formed in the open spaces.
Permian pegmatites, both large and small, can be found cross-cutting all of Haddam’s bedrock. The larger ones intrude mostly the Middletown and Collins Hill Formations on both sides of the Killingworth Dome. They generally stand out as topographic ridges. Most of the feldspar quarrying took place in internally zoned pegmatites in the eastern belt of these rocks, especially at the Rock Landing and Gillette Quarries in Haddam Neck. The latter pegmatite, opened in 1895, contains miarolitic cavities that produced spectacular euhedral pocket crystals of elbaite, one of the few places in North America, plus abundant smoky quartz, albite, beryl, fluorapatite, topaz, microcline, and lepidolite crystals. It is the type locality for the lithian muscovite variety schernikite, named for early Gillette gem miner Ernest Schernikow. A similar pegmatite, the Sawmill Quarry, was worked on the west flank of Long Hill. Numerous small, cross-cutting pegmatites were encountered in the gneiss quarries working the Allen vein from Haddam Neck southward well into Long Hill. These narrow but sharply zoned pegmatites produced abundant gem grade aquamarine, plus schorl, almandine, columbite, and occasionally molybdenite. Some were worked for feldspar also. Pegmatites in the Higganum area are unzoned and simple, with reddish microcline that discouraged quarrying. Their main asset is abundant euhedral magnetite crystals.
In 1810 Archibald Bruce discovered chrysoberyl at the Cephus Brainerd house on Walkley Hill Road, the first place the mineral was found in-situ. This odd-ball rock consists of albite variety oligoclase, quartz, beryl, spessartine, schorl, chrysoberyl, cordierite, gahnite, columbite-(Fe), and talc and was studied for decades. The rock layer is conformable with the host rocks and lacks K-feldspar and so is more like a metamorphic rock and is unlike the true, cross-cutting granitic pegmatites in the area. Similar rocks composed mainly of oligoclase, quartz, cordierite and schorl are found elsewhere along strike at Tim’s Hill and at state Route 9 interchange 8. The presence of columbite-(Fe) is also noteworthy because the first crystal (named simply columbite) was described by Hatchett in England in 1802 and was collected perhaps 100 years earlier from an unknown Connecticut locality. The recognition of this new mineral lead to new finds in Haddam (first confirmed North American locality and Middletown, intense study, and speculation that the first crystal came from this area, perhaps from Nat Cook's columbite prospect.
The combination of varied bedrock; abundant simple to complex pegmatites; faulting; intense quarrying for stone, feldspar, and gems; and mineralogists at nearby universities made this small town famous in the mineral world, as related by traveling doctor Frederick Hall (1840):
Commodity ListThis is a list of exploitable or exploited mineral commodities recorded from this region.
Mineral ListMineral list contains entries from the region specified including sub-localities
115 valid minerals. 1 (FRL) - first recorded locality of unapproved mineral/variety/etc.
Rock Types Recorded
Rock list contains entries from the region specified including sub-localities
Select Rock List TypeAlphabetical List Tree Diagram
Entries shown in red are rocks recorded for this region.
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. 
|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.
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. 
Localities in this RegionShow map
- Middlesex Co.
- Almandine schorl and sillimanite locality
- Arnold Granite Quarry (General Brainerd Quarry; Great Hill Quarry; Hazelton Quarry; Haddam Quarry; Brookes Quarry)
- Arnold Quarry
- Beaver Meadow Road - State Route 9 Interchange
- Chrysoberyl locality
- Civilian Conservation Corps prospect (CCC prospect; Cook columbite prospect)
- Civilian Conservation Corps Quarry (CCC Quarry; Smith Quarry; Turkey Hill quarry lot)
- Gulf Quarry
- Haddam Neck
- Connecticut Yankee atomic power plant
- Feldspar quarry
- Gillette Quarry (J-J Mine; Haddam Neck Quarry)
- Graphite locality
- Knudsen prospects
- Quarry Hill (Brainerd Quarries; Shailor Quarries)
- Rock Landing Quarry (Capt. Rohrback Quarry)
- Tidewater feldspar quarry
- Unnamed amphibole-tourmaline-magnetite locality
- Hazen quarry (Epidote locality)
- Hewitt Gem Quarry (Herb's Gem Quarry; Sawmill Quarry)
- Middlesex Co.
- Middlesex Co.
- Hill above the parsonage
- Jail Hill Road locality (Jail Hill Quarry)
- John Salak Quarry
- Kelsey prospect (Parmalee farm)
- Lieser's Ledge
- Long-lot Quarry
- Long Hill (Turkey Hill) prospects
- Long Hill Quarry
- Long Hill quartz locality
- Magnetite locality
- Nathaniel Cook house
- Nemo's Quarry
- Roberts Mica prospect
- Sandy Hill
- Shailor Quarry
- State Route 9 rock cuts
- Sulfur Spring (Sulphur Spring)
- Thulite locality (Walkley Hill)
- Timms Hill (Tim's Hill; Iolite Hill)
- Tourmaline locality
- Ultramafic rock bodies
- Middlesex Co.