The elementary composition of the xylem is the following (%):

C 49.2; H 5.91; O + (N) 43.1; ash 0.79 (the estimated amount of nitrogen is 0.2-0.3%). According to our studies, the bark of black locust is rich in minerals. Its ash content amounts to 4.76% while that of the sapwood and the heartwood to 0.98% and 0.26%, respectively. Because of the large proportion of bark (20-25%) in locust firewood, 80-85% of the ash comes from the bark.

The cell walls of black locust consist of the following components: about 40-50% cellulose, 15-22% hemicellulose and 25-30% lignin.
Among the important extractives of black locust tannins can be mentioned.
The tannin content is 3-6% in the bark and 2-4% in the xylem; the respective values for oak are 5-10% and 3-7%.
In addition to tannin, dihydro-robinetin, with 2-5 weight-percentage in the heartwood, substantially contributes to the durability of black locust. This substance provides the typical greenish-yellowish-brow colour to black locust.
Crystalline deposits (calcium carbonate, calcium oxalate) can be found particularly in the rays, and occasionally in the vessels. This significantly increases tool wear when processing locust.