File:New Haven Arkose (Upper Triassic; Durham, Connecticut, USA) 4.jpg

English: Hematitic sandstone from the Triassic of Connecticut, USA. (public display, Geology Department, Wittenberg University, Springfield, Ohio, USA)

The Newark Supergroup is a thick, geographically-widespread stratigraphic unit in eastern USA. It is Late Triassic to Early Jurassic in age and represents sediments and some lava flows that filled up old rift valleys that roughly parallel the Eastern Seaboard of America. The rift basins formed in the Triassic when the ancient Pangaea supercontinent attempted to break apart, but failed. A successful breakup of Pangaea occurred during the Jurassic. Most of the basin-filling rocks are terrestrial redbeds - hematite-rich siliciclastic sedimentary rocks, such as conglomerate, sandstone, siltstone, and shale, deposited in nonmarine environments.

This is a nonmarine redbed sample - it's sandstone (exhibit signage says it's arkosic sandstone). It appears to have granules in addition to sand. The brick red color is from hematite (Fe2O3 - iron oxide).

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From exhibit signage:

New Haven Arkose

This block of red arkosic sandstone is typical of the famous "brownstone" used during the 1800s and early 1900s to build many townhouses in New York, Boston, Philadelphia, Washington, and other cities. It was also commonly used for tombstones. Note the mica flakes in the stone. Brownstone was quarried along the Connecticut River Valley and in the Newark Basin of New Jersey. This specimen is Late Triassic in age from Durham, Connecticut.

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Stratigraphy: New Haven Arkose, Newark Supergroup, Upper Triassic

Locality: unrecorded/undisclosed site at or near the town of Durham, western Middlesex County, southern Connecticut, USA

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For more info., see:

en.wikipedia.org/wiki/Newark_Supergroup