A strong disadvantage of this yarn is that it will crush and will not gain its resiliency after cleaning. Avoid buying cut-pile style with low density. It has great resiliency, however, it is expensive, it stains easily, and it fuzzes easily. Mohair and Silk are similar to Wool in that they too self extinguish with flame. Silk does not have the fuzzing problem that Wool has, but normally is only found in rugs.
Mohair comes from goats and is essentially similar to wool.
All three are considered protein fibers and will all degrade if cleaned with a high pH substance. Cellulose - Cotton, Sisal , Coir, Sea Grass, Abaca, and Raffia all come from plants. Jute could also be considered in this group, but is commonly used in the backing of very few carpets. Cotton is rare and sometimes not associated with the others. Sisal is the more popular and used to be popular as door-mat material.