One of the most valuable fabrics in the ancient world (which continued to be produced on a small scale into the last century) came not from silk worms but from mollusks. It was known as byssus or sea silk. According to Wikipedia:
Sea silk is an extremely fine, rare and valuable fabric produced from the long silky filaments or byssus secreted by a gland in the foot of several bivalve mollusks (particularly Pinna nobilis L.) by which they attach themselves to the sea bed.
. . . The shell, which is sometimes almost a
metre long, adheres itself to rocks with a tuft of very strong thin
fibres, pointed end down, in the intertidal zone. These byssus or filaments (which can be up to 6 cm long) are then spun and, when treated with lemon juice, turn a beautiful golden colour which never fades.
The cloth produced from these filaments can be woven even finer than silk and is extremely light and warm . . . It was said that a pair of woman's gloves could fit into half a walnut shell and a pair of stockings in a snuffbox.
The Manopello image, a beautiful artifact but probably not the veil of St. Veronica, is a byssus fabric.
Byssus enjoyed a vogue in China during the Han dynasty when it was imported from the Roman Empire. They called it "mermaid silk." (Wikipedia)