You may have a piece of SIRCA from the leading edge. I know that NASA was experimenting with it a few years ago. SIRCA = Silicon Impregnated Reusable Ceramic Ablative. It is not a true "ablative" -- When brand new it is white. After its first use the surface layer heats up and ablates to form a hard black surface which provides a standoff protecting the rest of the leading edge tile.
Thanks! My specialty is mission control/operations, not thermal design. It was given to me a few years ago.