Tuckahoe Marble

TUCKAHOE MARBLE
Official Name:	Inwood Formation
Location:	Westchester County, NY
Age:	Late Cambrian - Early Ordovician
Lithology:	Marble
NYC Examples:	Federal Hall, Brooklyn Borough Hall, Washington Memorial Arch, Grace Church

Based on an unpubished compilation map of the Manhattan Prong by P.C. Brock and P.W.C Brock

The Tuckahoe Marble lies within the Inwood Marble Formations which crops out across northern Manhattan, the Bronx, Westchester County, and western Connecticut.

Headstones carved from Inwood Marble from northern Manhattan (Marble Hill) and the Bronx (Kings Bridge) are found in Lower Manhattan's 17th-century Shearith Israel Cemetary, and 18th-century Trinity churchyard where the oldest Inwood Marble headstone with a legible inscription dates to 1723.

Shearith Israel Cemetary (1682-1828)
55 St James Street, Lower East Side

In 1822, deposits of high-quality white marble were discovered along the Bronx River between Tuckahoe and Eastwood in Westchester County. Tuckahoe Marble was used to construct grand early nineteenth-century NYC Greek Revival buildings such as Federal Hall (1830), and Brooklyn Borough Hall (1840), the Italianate Stewart's "Marble Palace" (1846)--New York's first department store--and the Washington Memorial Arch in Washington Square. Tuckahoe Marble was the single most important white marble deposit in America until the latter part of the 1800's, at which time reliable access to the extensive high-quality marble deposits of southwestern Vermont was established. Quarrying of Tuckahoe Marble ceased in 1930.

Brooklyn Borough Hall (1840)	Washington Memorial Arch (1895)

GEOLOGICAL FEATURES OF THE TUCKAHOE MARBLE

The Tuckahoe Marble is composed predominantly of medium to coarse-grained calcite (CaCO3) and dolomite (CaMg[CO3]2). This white marble also contains common porpyroblasts of tremolite (CaMg5Si8O12[OH]2). The crystals of this light-colored amphibole protrude from weathered surfaces as long crystals with rhombic cross-sections (see below). Diopside (CaMgSi2O6) occurs are irreglar pale green crystals. The mica phlogopite (K2Mg6Al2Si6O20[OH]4) is also common, and occurs as small tawny crystals, and irregular bands and blobs. Silicate-poor layers are metamorphosed dolomitic limestones, whereas the silicate-rich layers are the metamorphic equivalent of dirty dolomitic limestones (a mixture of clays, silt, and carbonate minerals).

The Tuckahoe Marble contains minor amounts of hematite and pyrite. Oxidation of these iron-bearing minerals cause the stone to turn orange-brown when the rock is exposured and weathers.

Coarse Calcite-Dolomite of Tuckahoe Marble
Federal Hall, Wall Street

Tremolite Porphyroblasts in Tuckahoe Marble
Federal Hall, Wall Street

Diopside Porphyroblast in Tuckahoe Marble
Federal Hall, Wall Street

Phlogopite in Tuckahoe Marble
Grace Church, East Village

ENVIRONMENT OF FORMATION
The history of the Tuckahoe Marble begins 500 million years ago in the Late Cambrian to Early Ordovician. At this time an ocean incursion swept over much of Laurentia (the ancient continent that forms the heart of modern North America) creating broad, marine platforms. Calcitic sediments accumuated in In this shallow, tropical environment, to form a a thick limestone sequence. In the Middle to Late Ordovician a volcanic island arc terrane collided with the southern margin of Laurentia. In the compressional event of the Taconic Orogeny, slices of Inwood platformal carbonate rocks were buried by more than 40 kilometers of rock, and the dolomitic limestones metamorphosed to form the Inwood Marble under very high pressure-temperature conditions (granulite facies). During the Devonian, a suite of small granite bodies intruded the New York City region. These granites reintroduced water to the dry diopsidic marbles, and caused new hydrous minerals to form. The tremolite in the Inwood Marble formed during this retograde amphibolite-facies metamorphic event.

Images adapted from: http://jan.ucc.nau.edu/~rcb7/globaltext2.html