handwoven floor covering from the Farāhān district, northeast of Arāk in western Iran, produced in the 19th or early 20th century. Like the rugs of Ser-e Band, Ferahans have been prized for their sturdy construction and their quiet, allover patterning. Most of them have a dark blue ground showing an endless repeat of the herāti design, in which a diamond lattice peeps through a tangle of blossoms and leaves. The colouring may be continuously varied within such a repeat, producing attractive changes in effect. In other carpets the repeat is the gul hannāʾ, or henna flower, with clusters of six blossoms at intervals. Medallion schemes also occur. The most customary border is the “turtle” (a pair of split arabesques) on a ground of erosive green—produced by use of a copper salt that causes the wool dyed with it to wear more rapidly than the portions dyed with other colours, resulting in a sculpted surface effect.