The Standard Malaysian Name for the timber of Eusideroxylon zwageri (Lauraceae). Occasionally, the tree is known as tambulian in Sabah, while the European trade name for this timber is Borneo ironwood. The timber is monotypic. The sapwood is bright yellow when fresh, darkens on exposure and is sharply defined from the heartwood which is light brown to almost bright yellow when fresh and darkens on exposure to deep reddish brown, becoming very dark brown or almost black with age.
Also know asn Belian (Brunei); Borneo Ironwood (European Union); Belian, Onglen, Tebelian, Tulian and Ulin (Indonesia); and Biliran, Sakian and Tambulian (Philippines).
The timber is exceptionally hard and heavy and it has been classified under Heavy Hardwood with a density of 835-1,185 kg/m3 air dry.
The timber is one of the most durable in the world.
The heartwood is extremely resistant to preservative treatment.
Texture is moderately fine to fine and even with grain fairly straight or shallowly interlocked.
The timber falls into Strength Group A (Burgess, 1958) or SG 2 (MS 544:Part 2:2001).
It is easy to work despite its high density and produces a smooth and often lustrous surface.
The timber seasons slowly with a tendency for checking and splitting.
Shrinkage averages 4.5%.