How to Identify Black Locust Wood (Robinia pseudoacacia)

Color ranges from pale greenish-yellow to darker brown, darkening to a russet brown with age. Grain usually straight, with a medium texture. End grain: Ring porous; earlywood pores in rows two to three pores wide, latewood in clusters and tangential bands; vessels large in earlywood, medium in latewood, tyloses abundant; parenchyma vasicentric and aliform; rays narrow to medium, normal spacing.

Janka hardness 1,700 lbf (side hardness: the force needed to embed a 0.444-inch steel ball to half its diameter). Specific gravity 0.69 at 12% moisture content, so a cubic foot weighs roughly 43 lb. Weight in the hand is one of the quickest checks: compare a piece of known size against a board you already know.

Black locust tends toward a green or yellow tinge versus osage orange's brighter golden-yellow that ages to medium brown; unlike osage orange, black locust shavings do not release a yellow water-soluble dye when soaked in water, and black locust's heartwood fluoresces under blacklight. The Osage Orange page has its own details.

No characteristic odor; heartwood fluoresces under blacklight, a helpful identification clue.

Fence posts, boatbuilding, flooring, furniture, mine timbers, railroad ties, turned objects, and veneer.

Mixed machining challenges due to density and hardness, though it responds excellently to lathe work and steam bending; has a moderate blunting effect on cutting edges; reported to cause eye and skin irritation and, less commonly, nausea.

Photograph a freshly cut or sanded face in daylight, not a finished or stained surface, since stain hides color and finish flattens grain. Add a close-up of the end grain: cut a clean end, wet it or sand it to 220, and shoot from straight on; pore pattern and rays are the most reliable marks. Put a ruler in frame. The app suggests the likely species; confirm with the end grain and weight.