Earthenware storage jar with a turquoise glaze, Western Iran or Iraq, 8th century. H: 40; Diam: c. 34 cm, Inv. no. 27/2003. © The David Collection.

Green-glazed jars like this one are among the oldest known from the Islamic period, and the type goes back to Sasanian and Parthian prototypes. The decoration was made both with simple incising and with applied ornaments that form a bunch of grapes, etc. Copper oxide is one of the cheapest raw materials used to color glazes and also one of the most widespread. When copper oxide is used in a lead glaze, it turns a lush, grass-green color, while it becomes more turquoise in an alkaline glaze.

The rather coarse clay jar was probably made in Iraq, but related pieces have also been excavated in western Iran and in Syria.