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Old Mine Plaza construction site, Trumbull, Fairfield Co., Connecticut, USA

Latitude: 41°17'28"N
Longitude: 73°13'51"W
A well-known construction site locality bordering the NW side of Old Mine Park (Hubbard) Tungsten Mine, both sites have a mineral assemblage unique to the state. The original development as a retail plaza was abandoned and in late 2009 construction began on a Home Depot store that was completed in January 2011.

This locality, like the neighboring Old Mine Park, is underlain by gently dipping amphibolite and marble. The amphibolite contains layers and boudins of green plagioclase (albite?) and quartz and very coarse-grained fan-shaped aggregates of pale greenish-white scapolite group with sulfides. Excellent specimens of fluorescent scheelite are found in the amphibolite cut along the east edge of the property, especially where it is altered to a pale gray-brown clinozoisite. The marble contains grossular and diopside.

Cross-cutting veins contain the same muscovite-topaz-fluorite var. chlorophane-quartz assemblage found in the surrounding area. Excellent pale green beryl crystals are found at the contact of cross-cutting calcite-scapolite-clinochlore-fluorite-sulfide veins with the amphibolite, which is metasomatically altered to scapolite-phlogopite along the contact. Heitner (1998) indicates the material recovered was beryl, with no mention of emerald. The report of true emerald from this locality remains controversial and any trace quantities of chromium or other coloring agents that might or might not exist in beryl from this locality do not yield true emerald color at this locality, although some unanalyzed beryls from this locality have a peculiar greenish yellow tinge.

There are many small brittle faults cross-cutting the host rocks and open cavities in the faults contain excellent poker-chip calcite, purple to green fluorite, sulfides, and quartz. One extremely rusty fault breccia with abundant pyrite was exposed near the center of the site.

One word of caution, much rock fill was brought in to grade the site over the years and some collectors unfortunately have contaminated the site with discarded material from other localities. Only minerals found in the host matrix rocks/fault zones should be listed.

References

Heitner, H. (1998): Window of Opportunity, Field Collecting at Trumbull, Connecticut, Rocks & Minerals, May-June, p. 198.

Mineral List

Actinolite
Albite
Almandine
Axinite-(Fe)
Azurite
Bavenite
Beryl
var: Emerald ?
Bornite ?
Calcite
Chalcopyrite
Clinochlore
Clinozoisite
Cuprite
Diopside
Epidote
Epsomite ?
Ferberite ?
Fluorite
var: Chlorophane
Grossular
Gypsum
Hedenbergite ?
'Hornblende'
Hübnerite
Hydrotungstite ?
Lepidocrocite ?
Limonite
Magnetite
Malachite
'Manganese Oxides'
Marcasite
Margarite ?
'Margarodite'
Melanterite
Microcline
Milarite
Muscovite
Opal
var: Opal-AN

Orthoclase
Pickeringite
Pyrite
Pyrolusite
Pyrrhotite
Quartz
Rozenite
'Scapolite'
Scheelite
Schorl
Siderite
Sillimanite
Sphalerite
Stilbite-Ca
Topaz
'Tourmaline'
Tremolite
Tungstenite
Tungstite
Wolframite
Zircon


60 entries listed. 49 valid minerals. 1 erroneous literature entry.

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Copyright © Jolyon Ralph and Ida Chau 1993-2011. Jobs in Connecticut, USA Site Map. Locality, mineral & photograph data are the copyright of the individuals who submitted them. Further information contact the Site hosted & developed by Jolyon Ralph. Mindat.org is an online information resource dedicated to providing free mineralogical information to all. Mindat relies on the contributions of hundreds of members and supporters. Mindat does not offer minerals for sale. If you would like to add information to improve the quality of our database, then click here to register.
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