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Skyhill Chert, Pennsylvania

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  • Skyhill Chert, Pennsylvania

    Skyhill Chert

    11-26-2020, 07:48 AM
    The name Skyhill was given by Jack Donahue to local collectors while he was excavating the Boarts site in Lawrence County, Pennsylvania. Other names include: Boarts Chert, Helderberg, and Mahoning Black.

    Donahue gives this color description of Skyhill. "The chert at the Boarts site varies from black (Munsell Color 7.5YR 2.5/0) through gray (10YR 6/1) to very pale brown (10YR 7/3)

    Below is a description of all three varieties.

    Skyhill Black The black variety tends to be vitreous and takes on a waxy luster after heat treating. Voids and fractures are absent of crystalline quartz and some samples contain deposits of iron oxide. The stone is opaque, even in thin lenses. The fracturing ability was probably good due to the large number of thin, well made artifacts recovered from local sites. Occasionally the black variety will be striated with white bands. Skyhill black tends to resemble Coshocton black but lacks the "white lightning" streaks and is not as vitreous.

    Skyhill Gray Skyhill gray is the most common variety. This stone is opaque and tends to resemble chert more than flint. On some artifacts both gray and black can be mottled together. However, this is rare. The fracturing ability was good due to the large amount of debitage found on workshop sites. This lithic can be compared to Nellie chert but Skyhill gray lacks the silvery coloration.

    Skyhill Brown This subtype is an opaque chert. Color varies from light tan through medium brown and occasionally both colors will be mottled together. Due to a lack of debitage Skyhill brown was not easily accessible or aboriginal people made minimal use of it.

    Donahue states. "At various valley slopes along the Mahoning River and Coffee Creek (a tributary of the Mahoning river) rocks of the Mercer formation, including the Lower and Upper Mercer limestone, are exposed. The Lower component contains a nodular chert while the Upper Mercer component can have up to two feet of bedded chert at its top. In this case prehistoric people would have an ample supply of chert. A relationship between Coshocton Black and Skyhill may be assumed since both occur within the Upper and Lower Mercer limestone of the Pottsville formation." It should also be noted that Skyhill outcrops in Mercer County PA.

    Distribution Skyhill is a regional lithic used primarily in Mercer and Lawrence Counties in PA but has a distribution over a much wider area form Lake Erie south to Pittsburgh and from Clarion County PA west to Youngstown Ohio. Obviously the further you get from the source the less you encounter it.

    Pic 1 is the black variety
    Pic 2 is the gray
    Pic 3 is the tan/brown (the top point was the first arrowhead I found)
    Pic 4 is the entire group.





    Information and photo examples provided by paohrocks
    Searching the fields of Northwest Indiana and Southwestern Michigan
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