Materials Example 3, AMNH DN/305
Double Notched Butterfly bannerstone; Ohio, banded slate, h. 7.5, w. 11.5 cm
Metamorphic, banded slate is the most common rock used for the making of bannerstones. It is commonly found in glacial deposits around the Great Lakes or along the Ohio River Valley. Its relative softness is one reason for its common use. With slate, the sculptor could more precisely carve the thin wings of the Butterfly or Crescent forms as well as drill the central perforation. Another reason why slate was so often chosen for bannerstone construction is the natural banding that often occurs with slate, which is the result of shale and other materials metamorphosized together during glaciation. The bannerstone makers often chose eccentric examples of these graphic rocks that have added trace fossils or mineral inclusions that play an active role in the final composition. AMNH DN/305, a Double Notched Butterfly, is an excellent example of a carefully chosen banded slate rock for bannerstone carving. A photographed detail of these rust and white inclusions as well as the trace fossil tracks highlight natural elements of the rock that attracted the sculptor. Looking at the overall composition of the completed bannerstone, it is clear that the sculptor carefully centered their composition on the three included rust and white elements that move diagonally across the Butterfly shape of the sculpted stone.