An Early Islamic Rock Crystal Amulet Seal from Unguja Ukuu, Zanzibar

Archaeological excavations at Unguja Ukuu recovered a rock crystal cabochon seal with the word lillāh (“for God”) inscribed in the Kufic script on its domed surface. The artifact is an intaglio amulet seal engraved in the negative. Microscopic examination of the seal surfaces reveals that a rotary tool was used to make the initial inscription. At some later point, a diagonal spall was removed across part of the inscription. The diagonal spall appears to be along a natural crystal plane. It is impossible to determine if this was the result of intentional defacement or an accidental process that might have resulted in the eventual deposition of the seal. Strata dated by radiometric and relative methods coupled with the style of the Kufic script date the seal to the late-8th to 9th centuries CE. This artifact is the earliest known example of an Islamic amulet seal and of writing in the Zanzibar Archipelago.