You have one of two choices for quality rugs, really; there is wool, and everything else.
Wool has been the standard of quality and durability for thousands of years.
Wool is one of the most durable fibers on the planet; it sheds water, it holds dye extremely well, and it's fire retardant.
It's not uncommon to see wool rugs handed down through the generations, and wool rugs are commonly found that are hundreds of years old.
Wool's unique properties mean that often, these rugs look better after a century of use than they do when they're first woven.
Wool is extremely dense, which means that you can place a wool rug on sandy ground, and when you're done, just dust it off.
As a matter of fact, this is what Persian rug makers have been doing since the advent of rug making.
Wool rugs were the flooring of choice in the nomadic tents of the Persian tribesmen, for just that reason.
They don't mildew or stain easily, and they are extremely durable.
They can absorb the heaviest humidity, keeping rooms cooler and more comfortable for occupants.
Because of wool's long history and heavy demand in the rug trade, rug makers have had to find alternative sources for their wool.
Sheep are, of course, the wool of choice, but rug makers have also been using the increasingly popular Alpaca wool to supplement their wool of choice.
It's even becoming popular to mix the two creating a blend that is easy to maintain, and beautiful to look at!