Sock fabric is weighted nicely and just slightly opaque.  The fabric is almost heavy duty considering what it is.  Heavy duty as far as wear goes.

One Year Later - I re-ordered this sock and am happy to report the quality is still wonderful. I ordered several pair last year. The socks wash and dry nicely,wear well, and keep their color.  There is no built in heel box which makes the sock work for many body types and shoe sizes and it doesn't bunch down in the boot. The sock fits my plus size muscular legs very well.
This sock is probably not a boot sock for cold weather hiking but works perfectly well for casual and work wear.