Minerals of the Ellis Street Extension Road Cut

By Scovil, Jeffrey A

ROUTE 72

NEW BRITAIN, CT

When the Ellis Street Extension was constructed in 1973-75, its road cut produced numerous well-crystallized specimens of chalcopyrite, quartz, datolite, and barite, among others. The road cut exposed basalts with mineralized gas cavities and shrinkage cracks. In addition, quartz-carbonate-barite (QCB) veins were found in both the basalt and enclosing sandstone. Although the occurrence was not unique for Connecticut, this type is seldom found outside of the northeastern United States.

LOCATION

The road cut is south of the intersection of Ellis Street and the Ellis Street Extension of State Route 72 in New Britain, Connecticut, on both sides of the extension. The area, in central Connecticut, can be located on the 7.5-minute New Britain topographic quadrangle (U.S. Geological Survey 1996), and on the U.S. Geological Survey 7.5-minute geologic map GQ-494 (1966). The cut is easily reached via Route 72 from the south or from Ellis Street. However, collecting has not been allowed since construction was completed.

HISTORY AND WORKINGS

Specimens from the road cut were brought to my attention in 1973, but I did not visit the locality until fall 1974. The locality became well known to collectors from all over the state and was often the site of frantic collecting on weekends by entire mineral clubs. Blasting ceased in spring 1975, and the bottoms of the cuts were graded, effectively ending collecting. The locality consisted of two exposures, one approximately 300 feet long by 50 feet in maximum height, on the west side of the extension. The other, on the east side, was about 400 feet long and 30 feet high. The exposures are still visible on either side of the Ellis Street Extension and have been expanded substantially by subsequent highway construction.

PARAGENESIS

There are two types of mineralization at the Ellis Street Extension road cut. The basalt contains gas vesicle deposits of quartz, datolite, minor zeolites, and barite. Cutting through both the basalt and the arkosic sandstone country rock were hydrothermal QCB veins up to 1 meter wide consisting primarily of massive white barite. Cavities occurred mostly along the contacts with the enclosing rock and contained fine Herkimer-like quartz crystals, barite, and sulfide minerals.

One major vein and several minor veins occurred in the northeast part of the road cut. In this group of veins, the primary sulfide mineral was chalcopyrite. First to be deposited within these QCB veins was quartz as a drusy lining, followed by massive barite deposition forming the bulk of the veins. Before barite deposition ceased, a hydrocarbon, dolomite, second-generation Herkimer-like quartz, then chalcopyrite precipitated. Next came calcite, marcasite, galena, and copper. The final stage of crystallization produced malachite and barite microcrystals.

In the southwest side of the road cut, there was one small QCB vein in which bornite, the primary sulfide, occurred with minor chalcocite. In these bornite-bearing veins, the paragenesis was simpler-quartz, barite, dolomite, bornite and chalcocite, azurite, and finally malachite. The azurite and malachite resulted from oxidation of the bornite and chalcocite.

Mineralization of the basalts took place in gas vesicles and in some shrinkage cracks. A member of the chlorite group formed first as a pocket lining, tapered off, then reappeared at the end of the sequence. Anhydrite formed next and is evidenced by lamellar molds in the later-formed minerals. Calcite, analcime, prehnite, and datolite followed. Quartz crystallized throughout the period of deposition of the aforementioned minerals. Then came barite, orthoclase, hematite, and goethite.

GEOLOGY

The deposit occurs in normal faults cutting extrusive Hampden Basalt and arkosic sandstone of the East Berlin Formation of the Newark Group. Triassic deposits such as this occur in fault-bounded basins from Nova Scotia to North Carolina, often hosting superb secondary minerals. Well-known localities include those of Nova Scotia; Paterson, New Jersey; and Centreville, Virginia. The basalt is composed of augite and labradorite with accessory magnetite and olivine (Rodgers et al. 1959). Secondary minerals are found in vesicles and late fractures in the basalt. The sandstone is reddish- brown to maroon and relatively coarse grained. It contains angular fragments of quartz, fresh orthoclase, muscovite, and plagioclase.

Minor copper mineralization occurs in veins found in both the sandstone and basalt. The veins strike northeast and dip about 80[degrees] northwest. The sedimentary wall rock is only slightly altered, whereas the basalt wall rock is highly altered. Alteration of the basalt is typified by an inner albite-rich and an outer montmorillonite-rich zone. Chlorite, plagioclase, and magnetite- ilmenite intergrowths have been progressively replaced from the inner zone. Sedimentary rocks exhibit minor silicification and progressive hematite dissolution, resulting in a “bleached” gray sandstone as opposed to its unaltered reddish hue (Ryan 1986).

The QCB veins ranged in width from a few millimeters to 1 meter. No vein was exposed sufficiently in the workings to determine maximum length along either the strike or dip. Several small veins, about 15 cm in thickness, on the east side of the cut showed vertical zonation. Near the floor of the road cut, veins were primarily filled with massive white barite. When followed vertically, the barite ceased and the veins contained more open space. In these upper sections, the walls were lined with colorless, often doubly terminated scalenohedral calcite crystals to 4 cm long. At a higher level of the cut along its center, numerous mud-filled, but otherwise open veins were exposed that contained thousands of Herkimer-like quartz crystals. These veins had no particular orientation and appeared to occur in a severely brecci-ated area of the sandstone. Paragenesis in these quartz veins started with a druse of prismatic quartz, followed by ferroan dolomite, then the Herkimer-like quartz, which frequently completely enclosed the dolomite crystals. The dolomite was subsequently altered to very soft “limonite” that could easily be destroyed by cleaning.

Concerning the QCB veins, Ryan (1986) in his table 2 makes the following observations:

Open spaced filling, fairly regular zoning.

Vein/wallrock boundaries are sharp. Minor veinlets extend from the main veins into the wallrock. They are filled with quartz and/ or ferroan dolomite.

Quartz zones are the first precipitates along the wallrock. Zones are fairly monomineralic, clear or white. Widths range from 2 mm-9 cm. Grain size increases toward vein interiors. Quartz zones terminate at euhedral crystals.

Amorphous silica zones may occur in place of quartz or precede an interior quartz zone. Cherts contain thin laminae of red-black-gray domains paralleling vein walls.

Altered wallrock breccia is found sporadically throughout the quartz zones. Where breccia fills a vein, the quartz spans across as well in an interconnecting framework, coating each fragment.

Interior zones of ferroan dolomite, adjacent to silica zones, may or may not be present. Color is white-yellow, or golden-brown where oxidized. Texture is of interlocking grains ranging from prominently cleaved to mottled and uncleaved. Some subzones of alternate white and yellow ferroan dolomite are observed.

Minor chalcopyrite, and bornite with very minor inter-grown chalcocite, are scattered in separate patches throughout the ferroan dolomite zones. Vitreous bitumen occurs as small scattered spherical droplets (~4 mm) or larger elongate patches (2-15 cm).

Ferroan dolomite is extensively oxidized along cracks and at barite zone boundaries.

Barite occupies most vein centers but is absent in some. Barite is coarse grained (2-10 cm), bladed or plumose, or in some cases medium to fine grained with interlocking or massive texture (0.1-2 cm). Barite sometimes occurs as minor vug filling in other zones. Barite zones are largely monomineralic with minor disseminated quartz (0.1-1 cm).

Calcite occurrence is very minor in the form of late-stage vug filling.

GENETIC HYPOTHESES

Numerous hypotheses have been made regarding the origin of the copper-bearing QCB veins. The origin of the mineralizing solutions may be the result of lower temperature residual solutions of the deep-seated magmatic body that produced the associated basalt (Lewis 1907; Bateman 1923). Evidence supporting this hypothesis includes the QCB veins’ usual association with the basalts, the uniformity of such deposits, the occurrence of copper in the basalt pyroxenes (Lewis 1907), finely disseminated copper sulfides (Wherry 1909), and native copper as occasional large masses within the basalt (Sassen 1978).

Ryan (1986) has hypothesized a nonmagmatic origin for the mineralizing solutions. He proposes the solutions were diagenetic brines (derived from the formation of the enclosing arkosic sandstones). These brines were moderately saline and enriched in carbon dioxide, silica, sodium, aluminum, calcium, barium, and copper. Deep burial and the prevailing high geothermal temperatures heated the brines to a tem perature in excess of 200[degrees]C. Faulting provided a means for these fluids to rise toward the surface. Mineral precipitation was a result of decreasing temperature and pressure. Quartz precipitated first, sealing the fractures and inhibiting further flow. This allowed an influx of near-surface waters that were the source of ferroan dolomite, lead, and hydrocarbons. Renewed faulting allowed the reentry of the earlier regional waters along with barite precipitation. Prof. Jelle DeBoer of Wesleyan University has proposed yet another hypothesis based on a nonmagmatic origin for the mineralizing solutions (DeBoer, pers. com., 1988). The source of solutions is essentially the same as that proposed by Ryan. What differs is the means of solution emplacement. DeBoer contends seismic activity, subsequent to the magmatic activity, caused solutions to ascend due to “seismic pumping.” During seismic (earthquake) activity, compression waves called “P” (primary) travel through the earth. When they reach the deep brine-saturated sediments, the sediments are compressible to some degree, but not the brine solutions. Similar to a sponge being squeezed, the brine travels through the sediments. The direction of travel was generally westward and upward following the bedding planes of the sandstone. The copper, zinc, and lead could have come from the sediments and may also have come from the basalt.

Peter Megaw (pers. com., 1995) states that the veins are similar to Mississippi Valley-type (MVT) deposits. In MVT deposits, ore fluids are inferred to come from reduced metal-laden “(Pb-Zn-Ba-F- minor Cu) brines (10-30 percent NaCl) driven out of sedimentary basins (at 100[degrees]-200[degrees]C) that combine with oxygenated, sulfate-bearing meteoric waters, with mineralization occurring in structurally controlled permeability networks (collapsed caves, dolomitized rocks, and so on).” In the case of the Ellis Street Extension deposits (and other similar deposits in the Triassic basin), the structural controls are the faults that were subsequent to the basalt emplacement. Other similarities include bleached sediments, similar mineralogy and paragenesis to MVT deposits, overall chemistry, the precence of hydrocarbons, and a good nearby source for the copper (the basalt).

Robinson (1994) notes that the origins of MVT deposits are unclear, as are the reasons for there being such large crystals of both galena and sphalerite in the Tri-State district. If lead and zinc come in contact with sulfide-ion-bearing solutions, rapid precipitation of galena and sphalerite would occur. This would mean the formation of many small, not large, crystals. To produce large crystals, a very slow introduction of sulfides is necessary. In brines, sulfur is typically in the form of sulfates and not sulfides, and lead and zinc, commonly occur in the form of chlorides. It is known that some organic compounds can convert sulfate ions to sulfide ions. When these sulfates are removed from solutions carrying dissolved calcium, magnesium, lead, zinc, and carbonate ions, then dolomite, galena, and sphalerite are precipitated.

Considering the rarity of galena and total lack of sphalerite at Ellis Street, there was little lead and no zinc in the source brines. There must have been, however, a fair amount of calcium and magnesium and large quantities of barium. The Tri-State deposits also contain quantities of hydrocarbons as do those of Ellis Street. These could have been the source of organic compounds that may have precipitated the sulfides and carbonates. Robinson also postulates that the sulfide may have been added in MVT deposits by the thermal decomposition of petroleum and aided by the bacterial reduction of sulfates. He also notes that fluid inclusions in MVP minerals are often saline. It would be interesting to test the content of fluid inclusions in crystals from Ellis Street. The MVT hypothesis is only slightly different from that put forth by Ryan (1986). It may be that the deposits at Ellis Street and others like them in the northeastern United States are miniature MVT deposits within nontraditional host rocks.

MINERALOGY

The attraction of the New Britain road cuts were their well- crystallized mineral assemblages. The veins and vesicle fillings in the basalt produced superb datolite crystals in excess of 2.5 cm on matrix. Fine scalenohedral calcite and amethystine quartz also came from the basalt.

Portions of the QCB veins consisted primarily of Herkimer like, doubly terminated, limpid quartz crystals to 6 cm. Crystals occurred individually on brecciated sandstone fragments, or in druses lining the vein walls.

Chalcopyrite crystals to 2 cm were found on drusy dolomite with barite, calcite, and micro-sized marcasite. These made showy specimens, although crystals that large were rare. Well-formed microcrystals of cuprite, azurite, malachite, barite, and galena also occurred, to the delight of micromounters. Similar veins throughout the Triassic basins of Connecticut and New Jersey have produced small quantities of silver. These veins have been shown to contain potentially significant concentrations of uranium (Gray 1982).

Twenty-four mineral species have been identified from the road cuts, not including the rock-forming minerals.

Native Elements

Copper, Cu, is found as microscopic, arborescent growths in cracks and cavities in the gray sandstone. The only direct associated mineral is drusy quartz. Cuprite was often found on the same samples but never in direct association.

Sulfides

Bornite, Cu5FeS4,was the primary sulfide in only one vein. It occurred in masses to 8 cm across and rarely as complex, superficially altered crystals to 0.3 cm.

Chalcocite, Cu2S, was reported intergrown with bornite (Ryan 1986). It is interesting to note that the primary copper ore mineral at the famous Bristol Copper mine was chalcoc-ite (Jones 2001), often found as superb, world-class crystals.

Chalcopyrite, CuFeS2, was the primary sulfide found in all but one of the QCB veins. Masses to 7 cm and fine crystals to 2 cm were found. Smaller crystals are sharp pseudotetrahe-dra, sometimes tarnished a bright steel-blue. Larger crystals were rough, apparently composed of numerous pseudotetra-hedra in subparallel growth. Frequent associates are galena, marcasite, quartz, dolomite, and barite. Fine chalcopyrite crystals overgrown by barite were exposed by breaking apart narrow barite-filled veins.

Marcasite, FeS2, was occasionally found on dolomite as microscopic, tabular, orthorhombic-appearing crystals. These crystals would sometimes form oriented overgrowths on the blue- tarnished chalcopyrite, making very striking specimens. There appears to be an epitaxic relationship between the two minerals.

Galena, PbS, occurred as octahedral to cuboctahedral crystals to 0.3 cm in size. Cube faces are sometimes cavernous with chalcopyrite overgrowths. Galena octahedra were also found growing directly on chalcopyrite along with the oriented marcasite crystals.

Similar veins in nearby road cuts are reported to contain tenantite, covellite, sphalerite, and greater amounts of galena. The galena has undergone some weathering, producing minor cerussite and pyromorphite.

Oxides

Anatase, TiO2, was found associated with quartz, chalco-pyrite, and chlorite in the QCB veins. It occurred as brilliant, tabular, pale yellow-brown crystals less than 0.25 mm. Ana-tase was rare in the road cuts (Marcelle Weber, pers. com., 1992).

Cuprite, Cu2O, occurred as individual octahedral crystals less than 1 mm in size and as arborescent growths of stacked octahedra. It formed on drusy quartz, with gray sandstone always the host rock.

Goethite, a-Fe+3O(OH), has been tentatively identified at the road cut and occurs as microscopic (about 0.1-mm) brown hemispheres on barite and datolite.

An unidentified hydrous iron oxide presumed to be goethite was found as pseudomorphs after ferroan dolomite. In the quartz zones of the QCB veins, the pseudomorphs form a druse, with individual crystals to 0.8 cm. The dolomite had formed on top of a druse of prismatic quartz microcrys-tals. Larger more equant quartz crystals then formed on top of the dolomite, which was subsequently altered.

Hematite, Fe2O3, occurred as rusty-brown rosettes of microcrystals in the basalt vesicles. The rosettes are found on either datolite or quartz.

Carbonates

Aragonite, CaCO3, was found rarely as typical prismatic microcrystals on the iron oxide pseudomorphs after ferroan dolomite in the QCB veins.

Azurite, Cu3(CO3)2(OH)2, only in the bornite-bearing QCB vein, where lustrous microcrystals were found on drusy quartz. When associated with malachite, the azurite formed irregular colloform druses directly on clay in the cavities.

Calcite, CaCO3, typically formed scalenohedral crystals in both the basalt and the QCB veins. Milky white, doubly terminated crystals to 2.5 cm were found in cracks in the basalt, many coated with iron oxides. Scalenohedra were found with cavernous faces in druses in the basalt. One cavity yielded micro-sized scalenohedra capped with oriented rhombohedra, forming scepters. Equant crystals bounded by the rhombohedron were found lining cavities in the basalt.

Calcite was seldom found with the sulfides. When it was, it formed scalenohedra terminated by rhombohedra, perched on dolomite. Calcite was found in greater quantity where the veins graded into mostly barite and calcite and few sulfides.

Dolomite, CaMg(CO3)2, is ferroan (Ryan 1986) and occurred in both the basalt and QCB veins as typical saddle-shaped tan to ivory rhombohedra to 0.6 cm.

Malachite, Cu2(CO3)(OH)2, in association with bornite and chalcopyrite formed groups of radiating and matted needles. A strange occurrence in the bornite viens was malachite in vermiform habit. Some of these forms curled back on themselves, forming nearly complete rings.

Similar “rings” occur at the Schuyler mine in North Arlington, New Jersey (Jack Troy, pers. com., 1989). They have also been found at the Boston Road Prospect north of Hancock, Michigan, and the Isle Royale mine, Houghton, Michigan. Malachite also formed individual hemispheres associated with the secondary barite microcrystals in the chalcopyrite-bearing QCB veins. Hydrocarbons

Found in the QCB veins were jet-black spheres of a hydrocarbon to 1.3 cm in diameter, with a glassy luster and conchoidal fracture. Collectors referred to the hydrocarbon as “albertite,” though it may be more properly called vitreous bitumen.

It has been theorized (Gray 1982) that these spheres were droplets of oil suspended in the mineralizing fluid. During deposition of the vein minerals, these droplets were trapped and eventually polymerized, turning hard and glassy.

Silicates

Analcime, NaAlSi2O6?H2O, was one of only two zeolites found infrequently in the basalt. It was one of the first minerals formed and was completely covered by datolite.

Chlorites

An unidentified member of the chlorite family was the first to form as a dark green lining in gas vesicles in the basalt.

Datolite, CaBSiO4(OH), formed beautiful yellow-green crystal groups in the basalt, with individual crystals reaching 2.5 cm. A datolite-rich zone was encountered that produced many fine specimens for a period of several weeks.

Laumontite, CaAl2Si4O12?4H2O, was reported by Miller (1986) as a rare mineral in the road cuts.

Orthoclase, KAlSi3O8, variety adularia, was found associated with datolite. It occurred as orange-pink clusters of crystals in cauliflower-like aggregates. Miller (1986) made the identification by X-ray diffraction analysis, stating that adularia was previously unknown in Connecticut Valley basalts.

Prehnite, Ca2Al2Si3O10(OH)2, though found in large quantities and fine quality at other basalts in Connecticut and New Jersey, such as Paterson, is rare at New Britain. The few specimens recovered were of pale greenish-yellow color, typically covered by datolite.

Quartz, SiO2, as doubly terminated Herkimer-like quartz crystals was found in abundance in portions of the QCB veins and the associated brecciated sandstone. Single crystals reached 6 cm in length and formed druses 50 cm across.

Most of the fine quartz was found in a 30-cm-wide vein filled with sticky red clay of unknown identity. The crystals lined the vein walls and occurred on breccia fragments of sandstone. This vein and others yielded thousands of crystals for diligent collectors. Smaller crystals (less than 2 cm) are transparent and sometimes amethystine. Larger crystals tend to be cloudier and less transparent. Amethystine quartz crystals to 2 cm across occurred lining cavitites in the basalt, with some of the crystals having druses of micro-sized hematite on them.

Sulfates

Anhydrite, CaSO4, was found in the basalt as easily cleaved masses and as typical, slightly radiating laths of a pale blue color. One specimen in my collection has 1.5-cm-long laths associated with calcite. Anhydrite was scarce at the road cuts, but numerous lath-shaped molds attest to its former abundance.

Barite, BaSO4, was the major sulfate found at the Ellis Street cuts and was frequently the primary mineral in the up to 1-meter- thick QCB veins. Opaque, white, wedge-shaped crystals to 15 x 15 x 2.5 cm came from cavities in the veins. Secondary barite consisting of gemmy, clear, pseudorhom-bohedral microcrystals was found with malachite only in the chalcopyrite-bearing QCB veins.

Barite was also found in the basalts as pale blue, prismatic crystals to 2 cm. Because of their habit and color, these barites were first mistaken for celestine by collectors.

Barite also formed pale pink, equant pseudorhombohe-dra on datolite with hematite and hemispherical goethite. In addition, the barite formed pale brown strings of tabular microcrystals on dolomite in the QCB veins.

CHEMISTRY OF THE DEPOSIT

There is little evidence of supergene enrichment, as shown by the dearth of secondary minerals and the presence of calcite in the deposits. If there had been descending sulfate and acid solutions, they would have dissolved the calcite (Bate-man 1923). Alteration of the ferroan dolomite may indicate deep preglacial weathering.

The solutions were originally low in iron. The majority of iron in solution may have been derived from the leaching of iron from the surrounding arkosic sandstones by the reducing ore solution. This hypothesis is supported by the fact that here, as well as at Bristol, Connecticut, and other similar localities, the host rock is a locally bleached sandstone.

With the reduced availability of sulfur through oxidation, native copper might precipitate due to a lack of suitable ions with which to combine. Distance from the source would also aid this deposition. This hypothesis seems to be supported by the occurrence of native copper at Ellis Street at a distance from the QCB veins in association only with the copper oxide cuprite. Evidently, the mineralizing solutions were low in copper, as copper minerals make up a very small percentage of the veins.

It should be noted that the QCB veins at Ellis Street rarely showed bornite associated with chalcopyrite. The one bornite- bearing vein described was situated to the south of the basalt extrusive and the chalcopyrite-bearing veins, which were on the north side of the basalt. Bateman (1923) states that the iron leached from the sandstones would cause the solutions to grade from cupric to cuprous, depending on the availability of that iron. This change in availability would result in the sequential depositions of copper sulfides, ranging from copper rich/iron poor to copper poor/ iron rich- bornite to chalcocite to chalcopyrite.

It may be that this progression of higher to lower copper content in the sulfides may just reflect the progressive depletion of copper in the ore fluids. It has been suggested that this progression is due to an increase in the availability of iron and its oxidizing ability. Copper has a much greater affinity for sulfur than iron, and so the latter would just not be incorporated to any great extent until most if not all of the available sulfur was tied up. It is also much more likely that the oxygen in meteoric water would be the source of oxygen than the reduction and solution of the small amount of iron oxides available from the sandstone (Megaw, pers. com., 1995).

Clues to temperatures of the solutions are provided by fluid inclusions in quartz crystals from the QCB veins. The cavities contain a liquid and frequently a movable bubble. During examination under a warm microscope light, the liquid vaporizes completely and fills the cavity. Upon cooling to room temperature, the gas reverts to a liquid. The liquid vaporizes at close to 32[degrees]C, the critical temperature of carbon dioxide. The bubbles change little in size over the short temperature range before vaporization (Willaim Hen-derson, pers. com., 1975). Further studies on fluid inclusions in quartz (Ryan 1986) indicate that mineralizing fluids were moderately saline (9.5-13.0 weight percent NaCl equiva-lent) and deposited minerals within a range of 90[degrees]- 220[degrees]C. Homogenization temperatures were 88.5[degrees]- 172.5[degrees]C.

The origin of the large amounts of barite in this and similar deposits in the Triassic basin is unknown. Further south in Cheshire, Connecticut, the barite was plentiful enough to have been mined. In MVT deposits, the origin of sulfates is postulated to have been nearby evaporite deposits that added sulfates to the system through the influx of meteoric water (water derived from the surface). It is doubtful that there was enough iron leached from the enclosing sandstones to provide the amount of oxygen needed to produce the volume of barite present, whatever the source of the sulfates (Megaw, pers. com., 1995).

SUMMARY

During the short time the Ellis Street Extension was accessible, it produced many fine mineral specimens. The locality represents a unique association of mineral environments. Subsequent road work in the area exposed similar QCB veins (Miller 1986), and further road work will surely reveal more.

ACKNOWLEDGMENTS

I thank the following people for help in the preparation of this article: Dr. Robert Cook, Auburn University; Dr. Jelle DeBoer, Wesleyan University; Dr. Carl Francis, Harvard University; Dr. Norman Gray, University of Connecticut; Dr. William Henderson Jr.; Dr. Peter Megaw; Nyal Niemuth, Arizona Department of Mines and Mineral Resources; Les Wagner Jr.; and Marcelle and Charles Weber. William Besse prepared the map.

REFERENCES

Bateman, A. M. 1923. Primary chalcocite: Bristol Copper mine, Connecticut. Economic Geology 18:122-66.

Gray, N. H. 1982. Copper occurrences in the Hartford Basin of northern Connecticut. In Guidebook for fieldtrips in Connecticut and south central Massachusetts, ed. R. Joesteen and S. Quarrier, 195- 211. State Geological and Natural History Survey of Connecticut guidebook 5.

Jones, R. W. 2001. Famous mineral localities: The Bristol Copper mine, Connecticut. Mineralogical Record 32 (6): 433-50.

Lewis, J. V. 1907. Copper deposits of the New Jersey Triassic. Economic Geology 2:242-57.

Miller, F. W. 1986. Hydrothermal quartz and barite veins in the basalt of New Britain, Connecticut. In This is New England. War- wick, RI: Rhode Island Mineral Hunters.

Robinson, G. W. 1994. Minerals. New York. Nevraumont Publishing.

Rodgers, J., et al. 1959. Explanatory text for preliminary geological map of Connecticut, 1956. State Geological and Natural History Survey bulletin 84.

Ryan, S. 1986. Description and paragenetic interpretation of quartz-carbonate-barite veins of the Hartford Basin. Unpublished Master’s thesis, University of Connecticut, Storrs.

Sassen, R. 1978. The Chimney Rock quarry. Mineralogical Record 9:25-31.

Wherry, E. T. 1909. The Newark copper deposits of south-east Pennsylvania. Economic Geology 3:726-38.

JEFFREY A. SCOVIL

PO Box 7771

Phoenix, Arizona 85011

jeffscovil@earthlink.net

All photos by author of specimens from his collection

Jeffrey A. Scovil is a well-known professional mineral, fossil, gemstone, and jewelry photographer. See article showing his photos beginning on page 134.

Copyright Heldref Publications Mar/Apr 2008

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