Chain mail... but different. The links are "trefoil" knots--ordinary overhand knots, with the ends joined. Because of the configuration of the knots, the "rings" link together at 120-degree angles, forming an interesting hexagonal sort of pattern. This is a small sample, and the knots themselves are fairly small, making this altogether a rather wispy piece of mail, but very interesting.
For a larger sample of the same thing, see the Trefoil-x4 item in my shop.