Hand-knotted Heriz rugs are Persian rugs that originate in Heris and surrounding villages and areas of East Azerbayjan province in Iran (former Persia). Historically the region's sheep drank from water sources steeped in copper deposits (a trace element essential to a sheep's ability to produce good wool) which weavers credit as a reason for the quality of their rugs. Motifs include angular, stylized palmettes and central medallions; a rich color scheme is another characteristic of a Heriz rug. From the late 19th century, Heriz rugs were woven for export to the west. Traders often grouped all rugs from the region as Heriz including Gorevan (geometric weaves with longer pile and squared central medallions) and Bakshaish (abstracted and geometric adaptations of tribal and traditional Persian motifs). Although only sixty miles from the renowned carpet city of Tabriz, the rugs made in Heris differ in design and technique. Heris and Sarab city are both located in Sarab county. Metropolitan Sarab was far larger and wealthier than Heris which may account for the high quality of Serapi rugs, which are similar in design to Heriz rugs but with less obvious color contrasts and a finer weave. A clear sky blue is often found in Heriz and Serapi rugs. Experts say both types of rugs were often woven in the same workshops thus eliminating the need for two separate categories. Nevertheless, in the US Serapi is usually the term used for the top quality antique, finely-woven Heriz rugs.