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Brigalow

Scientific name

Acacia harpophylla. Family: Mimosaceae

Other names

spearwood

Description

  • Medium-size tree to 24m with a spread of 4m. Diameter up to 0.6m.
  • Bark is deeply furrowed longitudinally and hard.
  • Bark is dark brown, dark grey to black.

Occurrence

  • Occurs inland from the coast to the central west of eastern Australia.
  • Extensively cleared in the past for agriculture. Remaining stands and vegetation associations have conservation status.

Appearance

Colour

  • Heartwood is commonly dark brown, but sometimes dark reddish-brown.
  • Sapwood is thin, yellow and quite distinct.

Grain

  • Close, relatively straight grain.

Uses

Engineering

  • Historically used for mining timbers.

Construction

  • Historically used for small heavy construction, fence posts and rails.

Decorative

  • Fancy turnery.
  • Walking sticks.
  • Furniture.

Others

  • Heavy axe and tool handles.
  • Fishing rods.
  • Formerly used for musical instruments such as fingerboards and bows.
  • Used by Aboriginal peoples for spear shafts, boomerangs and nulla-nullas.

Properties

  • Density: 1025kg/m3 at 12% content; about 1.0m3 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 according to AS 2082—2000: Timber—Hardwood—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 more than 40 years).
  • Durability in-ground: Class 1 (life expectancy more than 25 years).
  • Lyctine susceptibility: untreated sapwood susceptible to lyctine borer attack.
  • Termite resistance: resistant.
  • Preservation: sapwood will impregnate with preservative.
  • Seasoning: dries slowly with little degrade.
  • Hardness: very hard (rated 1 on a 6-class scale) to indent and work with hand tools.
  • Machining: firm but not difficult to work, although hard on tool edges; planes with a fine finish and takes a high polish; sanding dust can irritate your nose and eyes and may cause dermatitis.
  • Fixing: no difficulties using standard fittings and fastenings.
  • Gluing: satisfactorily bonds using standard procedures.
  • Finishing: readily accepts paint, stain and polish.

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, 2–5 radial rows, small, numerous, indistinct without lens.

Research and resources

  • Boland, DJ, Brooker, MIH, Chippendale, GM, Hall, N, Hyland, BPM, Johnston, RD, Kleinig, DA and Turner, JD 2006, Forest trees of Australia, 5th ed., CSIRO Publishing, Collingwood, Australia.
  • Bootle, K 2005, Wood in Australia: Types, properties and uses, 2nd ed., McGraw-Hill, Sydney.
  • Ilic, J 1991, CSIRO atlas of hardwoods, Crawford House Press, Bathurst, Australia.
  • Queensland Government, DAF 2018, Construction timbers in Queensland: properties and specifications for satisfactory performance of construction timbers in Queensland. Class 1 and Class 10 buildings, Books 1 & 2, Department of Agriculture and Fisheries, Brisbane.
  • Standards Australia, 2000, AS 2082—2000: Timber—Hardwood—Visually stress-graded for structural purposes, Standards Australia International, Strathfield, NSW.