- (archaic) Wood coal or charcoal, distinguished from mineral coal; lignite.
- 1821, Journal of the Academy of Natural Sciences of Philadelphia: Volume 2 (page 24)
- This clay formation, entirely unconnected with that of the Mississippi, and the lower part of the Arkansa, is of a blueish-grey, abounding in pyrites and xylanthrax, and is the active seat of those pseudo-volcanoes and their remains existing in the upper part of the Missouri territory.
- 1863, The journal of the British Archaeological Association: Volume 19 (page 321)
- There are two beads of much interest: a small cylindrical one of chrysoprase, and a large one turned out of a piece of xylanthrax, similar to that met with at Bovy, Devonshire.