Kork wool (also spelled kurk) is the finest grade of wool used in Persian rug weaving. The word comes from the Persian term for the soft, fine wool taken from specific parts of a sheep's fleece — primarily the underbelly, neck, and shoulder — where the fibers are naturally finer, softer, and more lustrous than wool from other areas.

Characteristics that make kork wool prized:

  • Very fine fiber diameter — significantly thinner than wool from the back or legs of the same sheep
  • Natural luster — kork wool has a distinctive sheen that gives Persian fine workshop rugs their characteristic glow
  • Excellent dye absorption — the fine fiber structure takes natural dyes deeply and evenly, producing rich color saturation
  • Soft hand — fine kork-wool pile feels notably softer to the touch than standard-grade wool
  • High yarn fineness — when spun, kork wool produces a finer yarn, which in turn allows higher knot densities and finer design detail

Where kork wool is used:

  • The finest Persian Kashan rugs — Kashan workshop production is particularly associated with kork wool
  • High-grade Nain rugs — many fine Nain rugs use kork wool in the pile
  • Quality Tabriz workshop pieces — particularly the finer grades
  • Fine Qum wool rugs — alongside silk in mixed-fiber Qum production
  • Premium Isfahan rugs — wool pile on silk foundation often uses kork wool

The distinction between kork wool and standard-grade wool is meaningful in serious Persian rug evaluation. A "kork wool Kashan" is a higher tier of Kashan production than a standard Kashan — the difference is visible in the sheen of the pile, the depth of the colors, the softness of the hand, and (usually) the level of design refinement.

Note that all sheep produce some kork wool — the difference is in how the fleece is sorted after shearing. In high-end workshop production, the kork is separated and reserved for the finest weaving. In commercial production, all wool from the fleece may be used together, which is part of why workshop kork-wool rugs cost significantly more than otherwise-similar pieces.

When buying Persian workshop rugs, asking explicitly about wool grade — particularly whether the pile is kork wool — is a meaningful quality differentiator that many casual buyers don't know to ask about.