1- From the viewpoint of shearing : 

Spring wool; sheared in the early parts of spring. Autumn wool: sheared in late autumn. To weave carpet and to supply worsted thread mainly his type of wool is used.

2- From the quality and color viewpoints :

quality of wool depends on such factors as delicacy (fineness) of its fibers, thickness, and length of fibers, strength, level of curlicue, employment of natural dyes, stainability, elasticity, and collapsibility of fibers. As an example the longer the length of fibers and the lesser their thickness, the higher the quality of wool produced of such fibers. Of course, it is worth mentioning that such factors as gender and age of the sheep, climatic conditions, type of nutrition and season of shearing effectively influence the quality of wool. All parts of the sheep’s body are not covered with the same quality of wool and if all the wool sheared from different parts of the body are mixed up, due to discrepancies of color quality, as well as texture and delicacy the wool will lack uniformness and purity. Natural colors of wool include white, dark white, yellow, dark gray, brown and black. No doubt the more white and uniform the wool the more will be its quality and during the dyeing operations, it will lead to a better quality of the processed wool.

One of the characteristics of arid areas like Iran is the diversiform of its wool which gives it an elasticity property i.e. keeping its original condition and recoil quality. This quality, not very much suitable for cloth weaving, however, is a very useful and important property in carpet weaving. In this manner, the carpet piles in such conditions as compression, washing … will keep their original condition and do not become feltly.

3- From the viewpoint of nature :

Two types of wool are available; natural and artificial. Artificial wool from the appearance point of view resembles natural wool however, based on durability, dye absorption, fineness, and other attributes it has nothing in common with natural wool.