How hard is Formosan Koa?

Formosan Koa has a Janka hardness of 2150 lbf (9,560 N), a USDA Forest Products Laboratory value at 12% moisture content. That puts it well above woods like hickory and close to jatoba, harder and denser than true koa.

Is Formosan Koa actually the same as Hawaiian koa?

No. Despite the trade name, Acacia confusa is a different species that is denser and has a different working profile, and it is not a koa substitute in any official sense. Mislabeling has been a problem, so reputable dealers keep A. confusa and A. koa clearly separated.

ExoticAcacia confusa

Formosan Koa

Not a koa substitute. Different tree, different density, different working.

Formosan Koa (Acacia confusa) is an exotic hardwood from Taiwan with a Janka hardness of 2150 lbf. Its heartwood runs golden brown to deep reddish brown, often streaked, and it is rated durable to very durable against decay and termites.

Category: Exotic
Janka: 2,150 lbf
Botanical: Acacia confusa
Shipped at: 6–8% MC

Acacia confusa Native to Taiwan ('Formosa')

Native to Taiwan ('Formosa').

Not a koa substitute in any official sense. Heartwood golden brown to deep reddish brown, often streaked.

Detail of Formosan Koa grain — figured wood texture, photographed at Raw Heartwood — A close read on the grain. Detail of this specimen

What you see.

Heartwood golden brown to deep reddish brown, often streaked. Looks enough like true koa to confuse a buyer — that is where the trade name came from. Pale yellow sapwood, sharp line. Color deepens and evens out with age and light.

Heartwood color detail of Formosan Koa (Acacia confusa)

Heartwood, this specimen

How the grain runs.

Straight to slightly interlocked. Occasional wave or curl in select boards. Medium uniform texture, good luster.

Closer detail of Formosan Koa grain figure

Closer in

On the bench.

Durable to very durable. Holds up to decay and termites. Notably better than true koa, which is only moderately durable. Machines, turns, and carves well. The density wants sharp tooling and decent horsepower. Glues and finishes well. Pre-bore for fasteners. Mild blunting on edges. None when dry. Reactions are uncommon. Acacia as a genus has plenty of sensitizers, so some workers do react. The bark and root carry DMT-class alkaloids, but the heartwood as lumber is not a hazard in normal work.

The numbers, looked at directly.

Janka Hardness

0lbf

9,560 N. Side-hardness — force to embed a half-inch steel ball halfway into the wood.

Average Dried Weight

0lbs/ft³

930 kg/m³. At 12% MC.

Specific Gravity

0.72/ 0.93 at 12% MC

Basic over green volume; second number at 12% moisture content.

Hardness, in context

A side-hardness measurement. Higher number, harder wood.

Shrinkage — radial / tangential / volumetric

3.0%radial

6.5%tangential

10.0%volumetric

On sourcing

Where this wood comes from matters.

Not on CITES. IUCN Least Concern. Naturalized in Hawaii, occasionally treated as a minor invasive in dry-to-mesic forests. Not on the state noxious weed list. Plantation and land-clearing supply in Hawaii, plus stock from Taiwan.

What it's for.

Furniture
Flooring
Turnings
Tool handles
Posts
Decorative woodware

Worth knowing.

Not a koa substitute in any official sense. Different species, denser, different working profile. Mislabeling has been a problem — reputable Hawaiian dealers keep A. confusa and A. koa clearly separated.

Sources & references.

Common questions.

How hard is Formosan Koa?: Formosan Koa has a Janka hardness of 2150 lbf (9,560 N), a USDA Forest Products Laboratory value at 12% moisture content. That puts it well above woods like hickory and close to jatoba, harder and denser than true koa.
Is Formosan Koa good for outdoor use?: Yes. It is rated durable to very durable and holds up well to decay and termites, notably better than true koa, which is only moderately durable. The body lists posts among its uses.
Is Formosan Koa actually the same as Hawaiian koa?: No. Despite the trade name, Acacia confusa is a different species that is denser and has a different working profile, and it is not a koa substitute in any official sense. Mislabeling has been a problem, so reputable dealers keep A. confusa and A. koa clearly separated.

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