What is the most durable hardwood floor available?

The short answer is Brazilian Walnut with a Janka rating of 3680. The long answer is, all hardwood flooring is very dependable and resilient, and the quality of the finish on top of the floor is the most important factor in durability. Different species do have different hardness ratings. Although species do have different hardness scales, you would not notice any appreciable differences from one to another in your wood floor under normal wear.