If it's light weight and for a summer quilt, it could be.....wool!!!
Wool breathes, is cool in summer, warm in winter. And it quilts like butter left on the counter in July with no air conditioning. You can quilt it to death and it doesn't get stiff.
I haven't tried the bamboo yet (I've heard good things from the other LAers), but it is on my list to try next time I place an order.