Brigalow

Scientific name

Acacia harpophylla. Family: Mimosaceae

Local names

Brigalow, spearwood

Description and natural occurrence

A medium-sized tree to 24 m with a spread of 4 m. At its best it attains a diameter of 0.6 m.

The bark is deeply furrowed longitudinally, hard, dark brown, dark grey to black. Brigalow occurs from the immediate inland to the central west areas of eastern Australia.

Brigalow stands have been extensively cleared for agriculture in the past, and current remnant stands forming vegetation associations of considerable conservation interest.

Wood appearance

Colour. Heartwood varies from dark reddish-brown to, more commonly, dark brown. The sapwood is thin, yellow and quite distinct.

Grain. Close-grained. Relatively straight grained.

Wood properties

Density. 1025 kg/m3 at 12% content; approximately 1.0 m3 of seasoned sawn timber per tonne.

Strength groups. S1 unseasoned; SD1 seasoned.

Stress grades. F14, F17, F22, F27 (unseasoned), F22, F27, F34 (seasoned), when visually stress-graded in accordance with AS 2082-1979, Visually stress-graded hardwood for structural purposes.

Joint groups. J1 unseasoned; JD1 seasoned.

Shrinkage to 12% MC. 4.7% (tangential); 2.6% (radial).

Unit shrinkage. 0.39% (tangential); 0.28% (radial). These figures apply to timber reconditioned after seasoning.

Durability above-ground. Class 1 - life expectancy over 40 years.

Durability in-ground. Class 1 - life expectancy over 25 years.

Lyctine susceptibility. Untreated sapwood susceptible to lyctine borer attack.

Termite resistance. Resistant.

Preservation. Sapwood accepts preservative impregnation.

Seasoning. Dries slowly with little degrade.

Hardness. Very hard (rated 1 on a 6 class scale) in relation to indentation and ease of working with hand tools.

Machining. Firm but not difficult to work, although hard on tool edges. The sanding dust can be an irritant to nose and eyes and may cause dermatitis. Planes with a fine finish and takes a high polish.

Fixing. No difficulties have been experienced with the use of standard fittings and fastenings.

Gluing. Can be satisfactorily bonded using standard procedures.

Finishing. Will readily accept paint, stain and polish.

Uses

Engineering. Has been used for mining timbers.

Construction. Has been used in the past for small heavy construction, fence posts and rails.

Decorative. Fancy turnery, walking sticks and furniture.

Others. Heavy axe and tool handles, fishing rods; formerly used by Aborigines for spear shafts, boomerangs and nulla-nullas. Has potential for musical instrument and accessories manufacture, such as fingerboards and bows.

Identification features

General characteristics

Sapwood. White to yellow, with distinct heartwood boundary.

Heartwood. Dark brown, chestnut brown, often variegated.

Texture. Fine, interlocked grain.

Wood structure

Vessels. Solitary, and radial rows of 2-5, small, numerous, indistinct without lens.

Further reading

Boland, DJ, Brooker, MIH, Chippendale, GM, Hall, N, Hyland, BPM, Johnston, RD, Kleinig, DA and Turner, JD 2006, 'Forest trees of Australia', 5th edn, CSIRO Publishing, Collingwood Australia.

Bootle, K 2005, 'Wood in Australia: types, properties and uses', 2nd edn, McGraw-Hill, Sydney.

Hopewell, G (ed.) 2006, 'Construction timbers in Queensland: properties and specifications for satisfactory performance of construction timbers in Queensland, Class 1 and Class 10 buildings', books 1 and 2, Department of Primary Industries and Fisheries, Brisbane.

Ilic, J 1991, 'CSIRO atlas of hardwoods', Crawford House Press, Bathurst, Australia.

Standards Australia, 2000, 'AS 2082-2000: Timber - hardwood - visually stress-graded for structural purposes', Standards Australia.

Last updated 28 July 2010