Top portion is finished with water-base urethane; bottom with oil-modified polyurethane.

Color: Heartwood is yellow-brown when freshly cut, turning dark brown to almost black with alternate layers of light and dark. Sapwood is yellowish-white and clearly demarcated from heartwood.
Grain: Straight when quartersawn; coarse texture.
Variations within species and grades: Moderate variations in color.

Hardness (Janka): 1630; 26% harder than Northern red oak.
Dimensional Stability: Excellent (change coefficient .00201; 46% more stable than red oak). However, actual installations have demonstrated significant movement in use.
Durability: Average.

Sawing and machining: Difficult due to rapid dulling of tools; carbide tooling recommended.
Sanding: Sands satisfactorily.
Nailing: Good holding ability.
Finishing: Some solvent-based stains do not dry well.
Comments: Dermatological and respiratory allergic potential.
Information is from The National Wood Flooring Association
"Wood Species Used in Wood Flooring"