Common Name(s): Australian buloke, bull oak
Scientific Name: Allocasuarina luehmannii (formerly Casuarina luehmannii)
Distribution: Eastern Australia
Tree Size: 30-50 ft (9-15 m) tall,
1-2 ft (.3-.6 m) trunk diameter
Average Dried Weight: 69.9 lbs/ft3 (1,085 kg/m3)
Specific Gravity (Basic, 12% MC): 0.86, 1.09
Janka Hardness: 3,760 lbf (16,740 N)*
Modulus of Rupture: 18,850 lbf/in2 (130.0 MPa)*
Elastic Modulus: 2,682,500 lbf/in2 (18.50 GPa)*
Crushing Strength: 10,150 lbf/in2 (70.0 MPa)*
*Strength properties are estimated based on AS/NZS 2878:2000, strength group SD2
Shrinkage: Radial: ~5%, Tangential: ~9%,
Volumetric: ~14%, T/R Ratio: ~1.8
Color/Appearance: Heartwood is reddish brown. Somewhat well defined sapwood is a light yellowish brown. Very large aggregate rays produce a lace-like pattern on quartersawn surfaces. Rays are so large, some pieces have visible ray flecking on flatsawn surfaces.
Grain/Texture: Grain is straight to slightly interlocked. Uniform medium texture with good natural luster.
Rot Resistance: No data available.
Workability: Can be difficult to work on account of its hardness. Tearout can occur during planing or surfacing, especially on quartersawn surfaces in the rays. Turns and finishes well.
Odor: No characteristic odor.
Allergies/Toxicity: Besides the standard health risks associated with any type of wood dust, no further health reactions have been associated with Australian buloke. See the articles Wood Allergies and Toxicity and Wood Dust Safety for more information.
Pricing/Availability: Seldom available outside Australia. Occasionally available as small turning blocks or craft blanks. Prices are high for an imported hardwood.
Sustainability: This wood species is not listed in the CITES Appendices or on the IUCN Red List of Threatened Species. However, while the tree species itself may not be directly threatened by extinction, certain stands in Victoria and New South Wales are listed as endangered by the government of Australia.
Common Uses: Knife handles, flooring, fine furniture, and turned objects.
Comments: Australian buloke is commonly reported as the hardest wood in the world. This is based upon a single data source and may not give the best representation of all testing and data available. Consequently, with as many data points taken into consideration as possible, Australian buloke ranks at #21 overall on the poster Worldwide Woods, Ranked by Hardness. For more information, please consult the video discussion, Quest for the Hardest Wood in the World.
The rays in Allocasuarina and Casuarina species are so large, ray fleck is considered to be best displayed on flatsawn surfaces (most lacewood-type woods only achieve a respectable ray fleck when quartersawn). When sheoaks are quartsawn, the ray fleck can become too large and irregularly patterned for smaller pieces.
Not closely related to true oaks (Quercus genus), the etymology of the common name bull-oak is ambiguous. Both woods share a similar ray-flecked appearance on quartersawn surfaces.
Porosity: diffuse porous
Arrangement: exclusively solitary
Vessels: medium to large, moderately numerous; reddish brown deposits occasionally present
Rays: narrow and very wide aggregate rays; normal and very wide spacing (respectively)
Lookalikes/Substitutes: The wide rays serve to separate Allocasuarina from most other genera (except for the closely related Casuarina genus). See notes below. Additionally, having exclusively solitary pores (rather than a mixture of solitary and radial multiples) further serves to differentiate sheoaks from other hardwood species.
Notes: Australian buloke, along with most species contained in the Casuarinaceae family, feature aggregate rays that can be extremely wide—perhaps the widest of any hardwood family in the world. Even the larger rays of silky oaks and lacewood in the Proteaceae family pale in comparison to the aggregate rays found in Casuarinaceae.