These plaques have a significance beyond what their humble appearance suggests. The great polymath al-Biruni (983–1048) described jade, its origin in Khotan, its hardness and the difficulty of working it, and its various ‘magical’ qualities. Current academic opinion has it that jade only appeared in the Islamic world in the second quarter of the 15th century, under the Timurids and as a result of the vast steppe empire established by Genghis Khan 200 years earlier. These plaques – along with another group in the al-Sabah Collection in Kuwait – date to the Ghaznavid era, and so close to the time when al-Biruni lived. So far they represent the earliest use of jade in the Islamic world.