Well I never knew that

Colour - 'Don't swim out too far'

Mulberry silk (cultivated) thread is the strongest natural fiber in the world, making it incredibly durable. A silk fibre, the same diameter as one of steel, is stronger than steel. The mulberry silk thread is also rounder, finer and smoother than silk harvested from the wild where the silkworms have to eat whatever leaves and plants are available to them.

I have my eye on some Posh Yarn Mulberry Silk in sock weight that is up for Sale later today. Pity mulberry silk yarn's not suitable for socks (unless you're Norah Batty). But maybe with a pair of garters .........