in norther parts of NA (starting in US and continuing north!) its not uncommon to make wool socks out of worsted weight yarns
(LL Bean Boots, for one, presume you are going to be wearing think socks (boot liner socks) and leaves room!)
Socks can be made from almost any weight or fiber.
some are better, some are worse.
you feet sweat more than any other part of your body, and if the fiber used doesn’t breath–(ie doesn’t have the ability to absorb AND wick away moisture) your feet (and socks) can quicly feel clammy.
Silk has been used for thousand of years for socks… but silk is an interesting fiber… make a rope from silk fibers, and its stronger than a cable made from steel (one the same sized)
but rub silk? (as you might on back of heel, or ball of foot) and silk will wear away in no time (it has tensile strenth (its hard to brake the fiber) but it can easily be eroded or abraided (it is not resistant to rubbing!
alpaca is warm, and it wicks (like wool) but it doesn’t have wools memory. it can (silk too) stretch out… and stay stretched out…
Cotton, rayon and all the new rayons ([I]rayon being a process for turning vegetable matter (wood pulp in “real rayon”)in to a fiber --new rayons use other vegetable matter, (bamboo, soy beans, etc)[/I] --is similar to cotton… it is absorbant (and so so at wicking–not a bad choice, but not very warm.
What works depends a lot on what you need.
cotton socks are not the best choice for norther latitudes (especially in winter months!)
but acrylic is fine for open shoes in souther climates (where sweat could evaporate–)
alpaca is great for bed socks… (the lack of memory isn’t an issue if you are sleeping in them!)
silk is a luxury fiber… and fine for lightly uses socks…but not a good choice for socks for hiking!