Queens Tunnel Mineral Localities

Charles Merguerian

Updated 22 February 2006

Today, sparse bedrock exposures exist in westernmost Queens where subsurface excavation of the Queens Tunnel took place between 1996 and 1999. Although now largely covered by urban structures, a few bedrock exposures still can be found west of the tunnel, in Queens. This proves that "If a tree can grow in Brooklyn – a rock outcrop can be found in Queens". Suffice to say that bedrock exposures have not been overly helpful in portraying bedrock conditions before excavation of the Queens Tunnel. A collaborative effort by (Merguerian 1999, 2000, 2001, 2002; Merguerian, Brock, and Brock 2001; Brock, Brock and Merguerian 2001; Merguerian and Ozdemir 2003) has redefined the bedrock stratigraphy of western Queens based on detailed mapping and study of the Queens Tunnel rocks. The roughly five-mile long Queens Tunnel is segmented by one major 116.7° curve and three smaller curves (1.8°, 13.7°, and 26.5°). The hamster-leg shape of the tunnel (a NE-trending leg of 10,000’ and a NW-trending leg of 15,522’) offers the geologist a broad cross-sectional view of the geology of the region.

In the late Twentieth Century, Dukelabs geologists mapped the Queens Tunnel and spent some free time collecting minerals along fault zones and from pegmatites. Most of the minerals were found in individual and reactivated faults with NNE and NNW trends (Merguerian, 2002). The minerals described below were identified using a stereoscopic microscope and standard physical property tests (luster, color, hardness, streak, cleavage, crystal form, etc.) used by any self-respecting card-carrying geologist. We await x-ray and optical tests for an "idontknowite" identified stereoscopically.

The mineral locality descriptions provided below are keyed to mapped areas of the Queens Tunnel. For example, Station 162+92 is found 16,292' away from the main shaft (19B) at Maspeth. Stationing starts at Shaft 19B in Maspeth and increases northeastward for 10,000' to Shaft 18B (Proposed) beneath Woodside. Clicking will bring you to a separate Gallery of Queens Tunnel Microminerals taken under the stereoscope and to a Gallery of Queens Tunnel Macrominerals taken with a digital camera. We hope you enjoy them. The hole through on 27 October 1999 marked and important event for the future of NYC municipal water flow (*and emergency plumbing contracts!)

Image: Courtesy Grow-Perini-Skanska, JV.

MINERALS OF THE QUEENS TUNNEL

Visit our Queens Tunnel Micromineral Gallery and our Queens Tunnel Macromineral Gallery

Updated 01 January 2006

Station # – Description

030+75 – Deep lime green drusy and microcrystalline epidote in veins up to 1 cm thick on a substrate of altered mafic gneiss.

077+85 – Upon a substrate of heulandite, cream-colored stilbite in hemispherical masses 2 cm wide and as felted crystalline masses of single sheaf-like crystals. The stilbite is overgrown by calcite and by pyrite. Mineralization occurs in a NS-trending reverse fault cutting interlayered garnet-diorite orthogneiss and garnet amphibolite. Collected 9/9/99 and 2/8/00.

093+35, RW - Blue plagioclase euhedral 1-2 cm crystals (sweats) in gabbroic gneiss cut by pegmatite and normal fault. Collected 10/12/99 .

~101+00 – Massive pyrite and quartz in a vein along NNW-trending fault.

~150+00 - Fallen block from left rib containing greenish radiating masses of prehnite overgrown with apophyllite, pyrite, and calcite crystals. Pointed out by Joe Brown and collected 6/15/98 .

~151+00 – Apophyllite with pyrite and calcite. Collected 6/10/98 .

~151+00 - Pyrite crystals in dacite host. Collected 6/10/98 .

162+30, RW - Stilbite forming a base with calcite crystals and cubic, clear chabazite microcrystals in a NNE-trending reverse fault zone. Collected 1/11/99 and 2/8/99 .

165+92, RW – Yellowish stilbite as a base to calcite crystals and drusy pyrite. The stilbite crystals, found in N20°E, 71°SE fault, grew as fibers perpendicular to the fracture. Collected 1/11/99 .

166+65, RW – Yellowish stilbite, calcite, and drusy pyrite crystals in N22°E, 77°NW-trending fault zone. Collected 1/11/99 .

167+00, RW & LW - Major 35’-wide NNE faulted pegmatite zone with box-work open cavities and greenish clay gouge. Megascopically, stilbite blades are overgrown by 2-3 mm spherical masses of pyrite. The multifaceted spherical masses are superceded by calcite crystallization, all on a fractured pegmatite or amphibole-gneiss matrix. Collected 10/6/98 , 11/24/98 , and 1/12/99 .

169+37, RW & LW - Open cavities in fault zone (N35°E, 68°NW) through amphibolite in garnet schist containing deep orange stilbite. The stilbite occurs in cavities a few cm in size as rounded sheaf-like clusters. Micro-scale pyrite cubes coat the stilbite. Some late-stage clear acicular stilbite blades occur locally. Collected 1/12/99 .

188+86, LW - Stilbite in sheaf-like crystal shapes at contact of pegmatite and biotite-chlorite schist. Another pocket located next to another pegmatite at 188+96, LW. Late plates of pyrite are found intergrown at late stages of stilbite mineralization. Collected 1/2/99 from conveyor belt during flooding incident and related 800’ conveyor walk-in.

190+15, RW - Light yellow crystalline stilbite crystals occur in gouge-rich fractured pegmatite. The stilbite crystals are overgrown on massive calcite. Two generations of small, clear crystals (apophyllite and younger analcime are predicted based on crystal shape) occur next. The analcime crystals are particularly striking because of their facet reflections and clarity. Locally, cm-scale pseudo-cubic calcite crystals are found to overgrow the crystallized matrix. Collected 1/20/99 and 6/7/99 .

190+52, RW - Clear interpenetrating calcite crystals about 1 cm in size in N11°E, 67°NW fault zone overgrow stilbite. Stilbite crystals form a basal substrate found overgrown with massive stilbite then the calcite. Late pyrite cubes here overgrow a second generation of clear stilbite blades. Collected 6/7/99 .

210+12, RW - Pegmatite matrix with openings containing microcrystalline epidote and chlorite, 4 mm tabular pink apophyllite(?), sphalerite, and stilbite. Collected 6/15/99 .

214+25, LW - Radiating masses of orange-colored stilbite surrounded by white calcite in fracture fillings related to a fault oriented N29°E, 72°SE. The fault, which cuts mafic gneiss, has produced a crush breccia zone up to 3 m wide. Mineralization is found in thin veins a few mm thick to irregular nodules up to 10 cm long, all within the brittle fault fabric. Collected 6/16/99 .