Mulga can be a small tree up to 9 m, with a well-defined main stem and angled branches, or a shrub 2 to 5 m tall with highly angled branches. The species has a very wide distribution, from Western Australia near Shark Bay, through central Australia to mid-west Queensland and New South Wales. It is rare in the Simpson and Great Victoria Deserts. Mulga grows in all states except Victoria and Tasmania. Mulga grows on flood and erosion plains and scattered on slopes and ridges. It is generally in low open woodland or tall shrubland, often in pure stands, but may be found with mallees, low shrubs and grasses.
Heartwood is dark brown, with contrasting markings of golden yellow, and very hard. There is a narrow band of yellowish sapwood. The wood is very close-textured.
Green density is the density of wood in the living tree, defined as green mass divided by green volume, and useful for estimating transport costs. It varies with season and growing conditions.
Air-dry density is the average mass divided by volume at 12 per cent moisture content (this is the average environmental condition in the coastal capital cities around Australia).
Basic density is oven-dry mass divided by green volume. This measure has the advantage that moisture content variations in the tree during the year are avoided.:
Green density is about 1330 kg/m3, air-dry density about 1200 kg/m3, and basic density about 1025 kg/m3.
Tangential and radial shrinkage are about 2.3 and 2.0 per cent respectively.
Goldfields craftsmen rate mulga as good for turning, machinability, drilling, screwholding and gluing, and excellent for sanding and finishing.
The CSIRO Durability Classes are based on the performance in ground of outer heartwood when exposed to fungal and termite attack.
|1||More than 25|
|2||15 to 25|
|3||8 to 15|
|4||Less than 8|
The ratings are not relevant to above-ground use. In late 1996, CSIRO published revised ratings, which include termite susceptibility. Ratings are now available for about seventy species for decay, and for decay plus termites.:
Although the durability has not been formally assessed, general use since settlement indicates that the species would be CSIRO Durability Class 1.
Minimum values (MPa) for strength groups for green and seasoned timber come from Australian Standard AS2878-1986 'Timber - Classification of strength groups'. In grading structural timber, each species is allocated a ranking for green timber of S1 (strongest) to S7, and for seasoned timber SD1 (strongest) to SD8.
MOR is modulus of rupture or bending strength, MOE is modulus of elasticity or 'stiffness', and MCS is maximum crushing strength or compression strength. Hardness refers to the Janka hardness test and is a measure of resistance to indentation.
Minimum values (Mpa) for green timber
Minimum values (Mpa) for green timber
Where test data were available, they are shown in bold print. Most values are from Bootle (1983), Wood in Australia. Types, properties and uses. (McGraw-Hill), or Julius (1906), 'Western Australian timber tests 1906: The physical characteristics of the woods of Western Australia'.
Where no strength data were available, air-dry density was used in accordance with the Australian Standard AS2878-1986 Timber - Classification of strength groups to predict the strength group. Consequently, the strength values quoted are from the above two tables.:
Green and dry strength groups are (S2) and (SD2). The brackets indicate conservative provisional ratings based on the air-dry density. The more important strength properties for those strength groups are listed in the table below.
|Modulus of Rupture||MPa||86||130|
|Modulus of Elasticity||MPa||14200||18500|
|Max Crushing Strength||MPa||43||70|
Fence posts are readily available, but sawn dried timber is difficult to obtain.
Major use has been as fence posts in Goldfields pastoral areas and in farming areas on the south coast of WA. The species is important for fence posts. The wood turns well and takes a high polish. Traditional uses included spears, clubs and boomerangs. Settlers used it for fencing because of its very high durability, and it is still used today. Other current use is for small ornamental articles for the tourist industry. The tree is important for fodder over a wide area of Australia.