Dolomitic marble (10.3 cm across at its widest)
Metamorphic rocks result from intense alteration of any previously existing rocks by heat and/or pressure and/or chemical change. This can happen as a result of regional metamorphism (large-scale tectonic events, such as continental collision or subduction), burial metamorphism (super-deep burial), contact metamorphism (by the heat & chemicals from nearby magma or lava), hydrothermal metamorphism (by superheated groundwater), shear metamorphism (in or near a fault zone), or shock metamorphism (by an impact event). Other categories include thermal metamorphism, kinetic metamorphism, and nuclear metamorphism. Many metamorphic rocks have a foliated texture, but some are crystalline or glassy.
Dolomitic marbles are crystalline-textured, ~monomineralic metamorphic rocks composed of dolomite (CaMg(CO3)2 - calcium magnesium carbonate). They form by metamorphism of dolostones. These rocks are identified by effervescing (bubbling) in acid when powdered. Some dolomitic marbles have a noticeable tremolite component (Ca2Mg5Si8O22(OH)2). A very similar metamorphic rock is dolomitized marble, which is a calcitic marble (metamorphosed from limestone) that has been subsequently dolomitized by the chemical addition of magnesium, introduced by hydrothermal fluids.
The dolomitic marble shown above is a clast derived from an Upper Pleistocene glacial till. It ultimately comes from the Precambrian of Canada.
Locality: Granville, Licking County, east-central Ohio, USA
Tags: dolomitic marble dolomite Precambrian till clast Pleistocene Ohio Canada
Dolomitic marble is a crystalline-textured metamorphic rock composed of dolomite or dolomite and calcite. Minor amounts of other minerals may be present. Dolomitic marble forms by metamorphism of dolostone or dolomitic limestones. A similar lithology with a different origin is dolomitized marble, which is a calcitic marble (having a limestone precursor) is chemically altered by fluids, resulting in dolomitization or partial dolomitization.
The sample seen here is from the Inwood Formation, a marble-bearing unit in the Cambro-Ordovician of New York State and adjacent Connecticut. Inwood marbles have been quarried as a source of cemetery headstones, building stone, and paving stone. Inwood marbles were originally marine limestones and dolomitic limestones. These precursor rocks were subjected to prograde metamorphism during the Ordovician-Silurian Taconic Orogeny and retrograde metamorphism in the Devonian. Commercial names for this material include "Tuckahoe Marble" and "Westchester Marble".
Stratigraphy: Inwood Formation / Inwood Marble, Cambrian to Lower Ordovician (= precursor age)
Locality: unrecorded / undisclosed site at or near the town of Thornwood (probably from an old quarry), southeastern New York State, USA
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Info. at:
en.wikipedia.org/wiki/Tuckahoe_marble
and
academic.brooklyn.cuny.edu/geology/powell/613webpage/NYCb...
Tags: dolomitic marble dolomite Inwood Formation Cambrian Ordovician Thornwood New York State Tuckahoe Westchester
Dolomitic marble is a crystalline-textured metamorphic rock composed of dolomite or dolomite and calcite. Minor amounts of other minerals may be present. Dolomitic marble forms by metamorphism of dolostone or dolomitic limestones. A similar lithology with a different origin is dolomitized marble, which is a calcitic marble (having a limestone precursor) is chemically altered by fluids, resulting in dolomitization or partial dolomitization.
The sample seen here is from the Inwood Formation, a marble-bearing unit in the Cambro-Ordovician of New York State and adjacent Connecticut. Inwood marbles have been quarried as a source of cemetery headstones, building stone, and paving stone. Inwood marbles were originally marine limestones and dolomitic limestones. These precursor rocks were subjected to prograde metamorphism during the Ordovician-Silurian Taconic Orogeny and retrograde metamorphism in the Devonian. Commercial names for this material include "Tuckahoe Marble" and "Westchester Marble".
Stratigraphy: Inwood Formation / Inwood Marble, Cambrian to Lower Ordovician (= precursor age)
Locality: unrecorded / undisclosed site at or near the town of Thornwood (probably from an old quarry), southeastern New York State, USA
---------------------------
Info. at:
en.wikipedia.org/wiki/Tuckahoe_marble
and
academic.brooklyn.cuny.edu/geology/powell/613webpage/NYCb...
Tags: dolomitic marble dolomite Inwood Formation Cambrian Ordovician Thornwood New York State Tuckahoe Westchester
Dolomitic marble is a crystalline-textured metamorphic rock composed of dolomite or dolomite and calcite. Minor amounts of other minerals may be present. Dolomitic marble forms by metamorphism of dolostone or dolomitic limestones. A similar lithology with a different origin is dolomitized marble, which is a calcitic marble (having a limestone precursor) is chemically altered by fluids, resulting in dolomitization or partial dolomitization.
The sample seen here is from the Inwood Formation, a marble-bearing unit in the Cambro-Ordovician of New York State and adjacent Connecticut. Inwood marbles have been quarried as a source of cemetery headstones, building stone, and paving stone. Inwood marbles were originally marine limestones and dolomitic limestones. These precursor rocks were subjected to prograde metamorphism during the Ordovician-Silurian Taconic Orogeny and retrograde metamorphism in the Devonian. Commercial names for this material include "Tuckahoe Marble" and "Westchester Marble".
Stratigraphy: Inwood Formation / Inwood Marble, Cambrian to Lower Ordovician (= precursor age)
Locality: unrecorded / undisclosed site at or near the town of Thornwood (probably from an old quarry), southeastern New York State, USA
---------------------------
Info. at:
en.wikipedia.org/wiki/Tuckahoe_marble
and
academic.brooklyn.cuny.edu/geology/powell/613webpage/NYCb...
Tags: dolomitic marble dolomite Inwood Formation Cambrian Ordovician Thornwood New York State Tuckahoe Westchester
(~7.1 centimeters across at its widest)
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Dolomitic marble is a crystalline-textured metamorphic rock composed of dolomite or dolomite and calcite. Minor amounts of other minerals may be present. Dolomitic marble forms by metamorphism of dolostone or dolomitic limestones. A similar lithology with a different origin is dolomitized marble, which is a calcitic marble (having a limestone precursor) is chemically altered by fluids, resulting in dolomitization or partial dolomitization.
The sample seen here is from the Inwood Formation, a marble-bearing unit in the Cambro-Ordovician of New York State and adjacent Connecticut. Inwood marbles have been quarried as a source of cemetery headstones, building stone, and paving stone. Inwood marbles were originally marine limestones and dolomitic limestones. These precursor rocks were subjected to prograde metamorphism during the Ordovician-Silurian Taconic Orogeny and retrograde metamorphism in the Devonian. Commercial names for this material include "Tuckahoe Marble" and "Westchester Marble".
Stratigraphy: Inwood Formation / Inwood Marble, Cambrian to Lower Ordovician (= precursor age)
Locality: unrecorded / undisclosed site at or near the town of Thornwood (probably from an old quarry), southeastern New York State, USA
---------------------------
Info. at:
en.wikipedia.org/wiki/Tuckahoe_marble
and
academic.brooklyn.cuny.edu/geology/powell/613webpage/NYCb...
Tags: dolomitic marble dolomite Inwood Formation Cambrian Ordovician Thornwood New York State Tuckahoe Westchester