YARN wikipedia (info)

A list of the materials that I use for my hats (and a short wikipedia information about origin, use and qualities): (I will add more materials)

HEMP: Hemp (from Old English hænep) is the name of the soft, durable fiber that is cultivated from plants of the Cannabis genus, cultivated for industrial and commercial (non-drug) use.
In modern times, industrial hemp has been used for industrial purposes including paper, textiles, biodegradable plastics, construction, health food, and fuel,[1] with modest commercial success.[2][3] In the past three years, commercial success of hemp food products has grown considerably.[4][5]
Hemp is one of the fastest growing biomasses known,[6] producing up to 25 tonnes of dry matter per hectare per year,[7] and one of the earliest domesticated plants known.[8] For a crop, hemp is relatively environmentally friendly as it requires few pesticides[9] and no herbicides.[10]
Cannabis sativa L. subsp. sativa var. sativa is the variety grown for industrial use in Europe, Canada, and elsewhere, while C. sativa subsp. indica generally has poor fiber quality and is primarily used for production of recreational and medicinal drugs. The major difference between the two types of plants is the appearance and the amount of Δ9-tetrahydrocannabinol (THC) secreted in a resinous mixture by epidermal hairs called glandular trichomes, although they can also be distinguished genetically.[11] Strains of Cannabis approved for industrial hemp production produce only minute amounts of this psychoactive drug, not enough for any physical or psychological effects. Typically, hemp contains below 0.3% THC, while Cannabis grown for marijuana can contain anywhere from 6 or 7 % to 20% or even more.[12]
Industrial hemp is produced in many countries around the world.[13] Major producers include Canada, France, and China. While more hemp is exported to the United States than to any other country, the United States Government does not consistently distinguish between marijuana and the non-psychoactive Cannabis used for industrial and commercial purposes.[12]

Cotton: Cotton is a soft, fluffy, staple fiber that grows in a form known as a boll around the seeds of the cotton plant, a shrub native to tropical and subtropical regions around the world, including the Americas, India and Africa. The fiber most often is spun into yarn or thread and used to make a soft, breathable textile, which is the most widely used natural-fiber cloth in clothing today. Mercerized cotton: Mercerisation is a treatment for cotton fabric and thread that gives fabric a lustrous appearance. The process is applied to materials like cotton or hemp.

Wool: The term wool is usually restricted to describing the fibrous protein derived from the specialized skin cells called follicles in sheep.[1]
Wool is taken from animals in the Caprinae family, principally sheep, but the hair of certain species of other mammals is also sometimes called "wool", including cashmere from goats, mohair from goats, vicuña, alpaca, and camel from animals in the camel family, and angora from rabbits.
Wool has several qualities that distinguish it from hair or fur: it is crimped, it has a different texture or handle, it is elastic, and it grows in staples (clusters)

Modal: Modal is a cellulose fiber made by spinning reconstituted cellulose from beech trees. It is about 50% more hygroscopic (water-absorbent) per unit volume than cotton. It takes dye just like cotton, and is color-fast when washed in warm water. Modal is essentially a variety of rayon. Viscose: Viscose is becoming synonymous with rayon, a soft material commonly used in shirt, coats, jackets, and other outer wear. Rayon: Rayon is a manufactured regenerated cellulose fiber. Because it is produced from naturally occurring polymers, it is neither a truly synthetic fiber nor a natural fiber; it is a semi-synthetic fiber.[1] Rayon is known by the names viscose rayon and art silk in the textile industry. It usually has a high lustre quality giving it a bright sheen.