In contrast, fibers from natural sources are provided by nature in ready-made form. Natural fibers include the protein fibers such as wool and silk, the cellulose fibers such as cotton and linen, and the mineral fiber asbestos. Plant fibers can be further on classified as:1  Fibre occurring on the seed (raw cotton, java cotton). 2  Phloem fiber (flax, ramie, hemp, jute).n contrast, fibers from natural sources are provided by nature in ready-made form. Natural fibers include the protein fibers such as wool and silk, the cellulose fibers such as cotton and linen, and the mineral fiber asbestos. Plant fibers can be further on classified as: