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Black & Gold Marble (Portoro Limestone, Upper Triassic; Porto Venere, Liguria, Italy) | by James St. John
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Black & Gold Marble (Portoro Limestone, Upper Triassic; Porto Venere, Liguria, Italy)

"Black and Gold Marble" from the Triassic of Italy.

 

In the commercial decorative stone trade, “marble” is used to refer to a wide variety of relatively soft rocks (H = 3 to 5) that will take a fine polish. These include true marbles and rocks that aren’t marbles, such as limestones, tectonic breccias, and serpentinites. True limestones are calcitic biogenic and ~chemical sedimentary rocks.

 

"Black & Gold Marble" is a Triassic-aged, black micritic limestone from northwestern Italy that has been extensively fractured (subsequently filled with white calcite veins), stylolitized, and partially dolomitized (= yellowish-brown material). This rock is derived from the Portoro Limestone of the La Spezia Formation (Rhaetian Stage, upper Upper Triassic, ~200-204 million years old), from exposures in the Tuscan Nappe of Italy's Apennine Fold & Thrust Belt. This material is quarried at Porto Venere in eastern Liguria, northwestern Italy.

 

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Taken on August 1, 2014