Gillette Quarry (J-J Mine; Haddam Neck Quarry), Haddam Neck, Haddam, Middlesex Co., Connecticut, USA

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The quarry named after its first owner, M. P. Gillette, was originally opened in 1896 for gem tourmaline, mineral specimens and commercial grade feldspar, and quickly produced a fair amount of elbaite. At this time in the eastern USA, only the pegmatites of Maine produced pocket elbaite crystals, so the abundant crystals from Gillette soon found their way into museums world-wide. It was closed by 1914 (some references from around that time call it the "Haddam Neck Quarry"), worked again for three months in 1934 by B. E. Johnson of Haddam, and finally by him and E. H. Johnson of Middletown (as the "J-J Mine") from November 1942 to November 1944. It has been idle since then, is on private residential property, and is not open to collecting.

According to Scovil (1992): "The workings consist of two open crosscuts leading to a very irregular open cut 108 meters long. These cuts expose a complex pegmatite consisting primarily of steeply dipping, interconnecting lenses that strike N 35° W. The pegmatite is exposed along its strike for about 100 meters, and varies in thickness from 5 to 25 meters. The walls of the pegmatite are characterized by irregular rolls or ridges most of which plunge gently north, and by sharp bends that are related to joints."

The pegmatite is complexly zoned and is lithium-bearing. Miarolitic pockets are most prevalent in the western cut. According to Sterling Gillette (1937) pocket size varied "from that of an egg or less up to a barrel or larger. The pockets were formed with an inside lining of quartz crystals and were usually about half full of decomposed rock formation. Always wet, the minerals found in the pockets were standing on end and unattached to any matrix. In some pockets there were found as many as 600 crystals of tourmaline ranging in size from that of a needle to that of a pencil or larger."

The quarry also is noted for a unique, pink, fibrous variety of muscovite called schernikite, usually forming parallel overgrowths on lepidolite and normal muscovite or as long, rhombic fibers coating and penetrating pocket crystals. Other noteworthy minerals are morganite overgrowths on cores of pale green beryl, often doubly-terminated by pinacoids and modified by pyramidal faces; amazonite; purple masses of lepidolite; euhedral gem fluorapatite; microlite; and topaz.

The wall rock consists of interbedded quartz-mica schist, mica-quartzite, calc-silicate gneiss and marble and minerals found there are included in the list below.

Cameron and others (1954) describes the zoning in the eastern and western portions of the pegmatite:

"Western part. - The sequence of zones inward from the walls, is as follows:
1. Border zone, ½ inch to 18 inches thick, composed of fine-grained quartz, [albite] plagioclase, muscovite, garnet and black tourmaline. The zone is present wherever the contact between pegmatite and wall rock is visible.
2. Wall-zone, sheet-mica bearing, ½ foot to 6 feet thick, composed chiefly of quartz and plagioclase with subordinate [microcline] perthite and muscovite and accessory green apatite and black tourmaline. Muscovite probably constitutes less than 5 percent of the zone. The unit is discontinuous and its distribution is best indicated by the geologic map.
3. Perthite-quartz zone, 10 to 45 feet thick, composed of white and salmon-pink perthite, pale green milky quartz, and graphic granite, with subordinate plagioclase and green muscovite (mostly books ¼ to 1 inch across), and accessory black tourmaline, green and rose beryl, red fluorite, apatite and lepidolite. Some of the quartz is granular (grain size ¼ inch) and occurs in branching, vein-like bodies which may have replaced other minerals of the zone. Albite, green tourmaline, green fluorescent apatite and green muscovite flakes are associated chiefly with the granular quartz. Cavities, 1 to 5 inches broad, are common only in this material. The cavities are lined with euhedral muscovite, albite and quartz crystals. At point A, several books of scrap muscovite, 1 inch broad and 5 inches thick, occur in a mass of granular quartz.

"Eastern part. - The walls of this part of the pegmatite in this area are characterized by deep rolls in places, especially northward from point D. The sequence of zones in this part of the pegmatite, inward from the walls, is as follows:

1. Border zone, ½ inch to 10 inches thick, similar to border zone in the western part of the pegmatite.
2. Quartz-plagioclase-perthite wall zone, 4 to 6 feet thick, composed of coarse-grained quartz, perthite and massive plagioclase with subordinate cleavelandite, black, green, and pink tourmaline, scrap muscovite and traces of pink lepidolite (some of the variety schernikite), pale green apatite, red fluorite, and green and rose beryl. The subordinate minerals commonly occur together in irregular masses in which are numerous small cavities. The unit is present for about 30 feet northward from point D. The zone was covered by water at the time of latest mapping.
3. Intermediate zone, sheet-mica bearing, 2 to 6 feet thick. This consists of quartz, plagioclase, perthite and muscovite with accessory garnet, black tourmaline and green apatite. The hanging wall part has an average thickness of 4 feet, and is more uniform in thickness and richer in mica than the footwall part. The zone is very lean along both walls of the pegmatite at the southern end of the quarry.
4. Quartz-plagioclase-perthite intermediate zone, 3 to 5 feet thick, composed of coarse quartz, subordinate plagioclase and perthite, and accessory black tourmaline and muscovite (books 1 inch broad). This zone is exposed only in the southernmost face of the cut, where it lies adjacent to both parts of the wall-zone.
5. Perthite-quartz intermediate zone, 4 to 20 feet thick, similar to the perthite-quartz zone of the western part but with less graphic granite and less granular quartz and associated minerals. Perthite occurs in larger masses; some are nearly pure anhedral crystals 5 feet long.
6. Quartz-perthite core, maximum thickness about 35 feet. About 85 percent of the unit consists of granular milky quartz (1/8 to 1 inch grains): coarse-grained (crystals 5 inches to 4 feet in diameter) white to pink perthite anhedra make up almost 10 percent. Green muscovite (books ¼ to 1/8 inch broad), black tourmaline, pale green apatite, and red fluorite make up the remainder of the zone. The margins of some of the perthite masses have replaced quartz and the minor minerals. No evidence could found, however, to indicate whether replacement occurred on a large scale at the expense of pre-existing pegmatite, or was merely a minor process in the development of the core."

Mineral List

Actinolite Albite var: Cleavelandite var: Oligoclase ? Almandine Annite 'Axinite' ? Beryl var: Aquamarine var: Goshenite var: Morganite Calcite Cassiterite Chalcopyrite Chrysoberyl

Columbite-(Fe) Cookeite Diopside Dolomite Elbaite Fluorapatite Fluorite Goethite Graphite Grossular ? Gypsum Hematite Kyanite ? Lepidolite Magnetite

Microcline var: Amazonite Microlite Group Molybdenite ? Montmorillonite ? Muscovite var: Schernikite (TL) Orthoclase Phlogopite ? Pyrite ? Pyrochlore Group Pyrolusite Pyrrhotite Quartz var: Rose Quartz

Quartz var: Smoky Quartz Scheelite Schorl Sillimanite ? Spessartine ? Sphalerite Spodumene ? Tantalite ? Titanite Topaz 'Tourmaline' 'var: Achroite' Uraninite ? Uranophane Vesuvianite

60 entries listed. 44 valid minerals. 1 type locality (other). 3 erroneous literature entries.

References

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