Siltstone, greywacke and conglomerate
These stones are common in the northern and central Eastern Desert. They
are types of sedimentary rock. One ancient quarry is known near the Wadi Hammamat.
Siltstone is often called wrongly slate.
the Hammamat siltstone is composed of silt-size grains; dark grey to greyish green colour; sand-size grains are not visible
Egyptian name: bxn
greywacke consists of fine sand grains with rare pebbles; dark grey to greyish green colour; the sand-size grains are still visible
many royal sarcophagi of the late Old Kingdom (Unas, Teti, Pepy I, Merenre) are made of greywacke
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