When it comes to building any structure made of wood, the kind of material used for the construction is crucial in ensuring the durability of the thing or building being made.
The kind of wood used for the construction often dictates the beauty of the final piece and how long it would last, even with regular use. But how hard is hard enough?
The answer depends largely on what the builder will use the wood for, but in general, the hardness of the wood means that even with regular wear and tear, the wood remains perfectly fine.
Despite the finish becoming scratched from regular use, the wood beneath the surface is intact and not rotting at all. This does not include the wood getting dented by some large force. But for most practical applications at home, a lot of hardwoods are really ‘hard enough’ to be used.
But the hardness of wood can be measured scientifically through the Janka hardness test, the most common one used for testing wood hardness.
The Janka scale rates the relative hardness of wood. This hardness scale rating has become the wood industry standard for determining whether a given wood is suitable for flooring material. Red Oak, which has a Janka rating of 1290, is the industry benchmark for comparing the relative hardness of different wood species.
The test measures how much force in Newtons (N) or pounds-force (lbf) is required to embed half the diameter of a 0.444″ (11.28 mm) diameter steel ball into the wood.
The larger the number, the harder the wood as it would require more force to embed the same size of the steel ball.
Builders looking for the hardest wood need to check out these top 10 known to be the hardest lumber in the world.
Though there are a number of small trees and shrubs that might have made it to this list, these were excluded from the list due to lack of practicality in using these as building materials due to unreliability of the material, lack of reliable documentation for use, and due to the unavailability of the wood because it is extremely hard to find or the tree is too small to yield a lot of usable materials.
10 – Cebil (Anadenanthera colubrina)
With the hardness listed as 3,630 lbf (16,150 N), Cebil ranks tenth on the list.
This wood is also known as the Curupay or as the Patagonian Rosewood; though the latter name is an exaggeration as this material is not a true rosewood.
The Cebil features a highly variable streaked appearance and has the lightest color in all the woods on this list.
Cebil has pale to medium reddish brown heartwood, frequently with darker brown to black streaks throughout. Color tends to darken with age. Sapwood is a pale yellow to pinkish brown; Irregular and/or interlocked grain; Fine uniform texture – Naturally lustrous; Rated as very durable and is resistant to termites, though more susceptible to other insect attacks. Generally hard to work with on account of its irregular grain and high density; has a pronounced blunting effect on cutters and turns well.
9 – Katalox / Wamara (Swartzia spp. / S. cubensis)
Under the Swartzia genus, the Katalox or Wamara might have a strange name but it’s got a hardness of 3,655 lbf (16,260 N), putting this ninth on the list.
What makes this wood extra special is that it offers wide variations to fit what the builder wants as some variants are reddish brown with black streaks while others could be as black as true ebony.
Katalox has dark reddish brown to nearly black heartwood, and sometimes with a strong purple hue. The Sapwood is sharply demarcated and is pale yellowish white. Pieces with curly or wavy grain are not uncommon; usually has straight grain, but can also be irregular or interlocked with a fine even texture and good natural luster; usually very durable. The Katalox’s heartwood is frequently considered to have a high resistance to decay and termites though susceptible to marine borers. Katalox is considered difficult to work on account of its high density; has moderate to high blunting effect on cutters, and if there is interlocked grain present, tearout can occur during planing. Can be difficult to glue because of its high density and natural oils present.
8 – Black Ironwood (Krugiodendron ferreum)
Although a hardwood with a hardness of 3,660 lbf (16,280 N), Black Ironwood rarely gets used to build homes and other large structures due to this material actually coming from trees that are too small to produce commercially viable wood.
However, this still makes it to the list due to the fact that enough wood could still be gathered to be used in small turning projects.
Black Ironwood’s heartwood can be a range of reds, oranges, violets, and browns; Pale yellowish white sapwood is clearly demarcated from heartwood; has a straight and even grain with a very fine texture and high natural luster. Known for it’s resistant to decay, and also resistant to termites. Workability wise, it has a high cutting resistance, and difficult to work due to density; it turns and finishes well.
7 – African Blackwood (Dalbergia melanoxylon)
Plenty of historical evidence suggest that the African Blackwood which has a hardness of 3,670 lbf (16,320 N) is actually the original ‘ebony’.
This wood is believed to have achieved ‘legendary status’ in many parts of the world for its beauty and hardness.
African Blackwood is commonly complete black, with little or no discernible grain; occasionally slightly lighter, with a dark brown or purplish hue; has pale yellow sapwood which usually very thin, and is clearly demarcated from the darker heartwood. Its grain is typically straight; fine, even texture and good natural luster; heartwood is rated as very durable in regards to decay resistance, though only moderately resistant to insects or wood borers. The lighter colored sapwood is commonly attacked by powder-post beetles and other borers; Workability wise: it is very difficult to work with hand or machine tools, with an extreme blunting effect on cutters. Most often used in turned objects, where it is considered to be among the very finest of all turning woods—capable of holding threads and other intricate details well. When made into clarinet or oboe bodies, the wood is typically processed on metal-working equipment, giving it a reputation as being metal-like in some of its working properties.
6 – Camelthorn (Vachellia erioloba)
The Camelthorn has been categorized into south African hardwood after spending years identified as a member of the Acacia genus.
Its wood has a hardness of 3,680 lbf (16,370 N) and often described as ‘stubbornly hard’. Huge giant thorns cover this tree, giving it its unique name.
Camelthorn usually has a dark reddish brown heartwood with a yellowish sapwood; has a Uniform medium texture and is rated as very durable and a good insect resistance. The wood is commonly used as fence posts, firewood, turned objects, and other small specialty wood objects.
5 – Verawood (Bulnesia arborea)
With its lovely feathery pattern and beautiful olive-green color, the Verawood is an excellent choice for wood material.
Not only does it offer a hardness of 3,710 lbf (16,520 N), this wood is also readily available and is quite inexpensive.
Verawood has a pale yellowish olive heartwood, to a deeper forest green or dark brown to almost black. The color tends to darken with age, especially upon exposure to light; has Pale yellow sapwood which is clearly demarcated from heartwood. When Quartersawn, the grain has a unique feathered pattern. The wood has straight to spiraled or slightly interlocked grain and has Fine even texture with very high natural luster. It is very durable for outdoor use and is said to last almost indefinitely in direct ground contact; also resistant to insect attack. Workability wise, it has tendency to skip over-top jointer cutters on account of its extremely high density, and very light passes are recommended; will also dull cutters, which overall considered quite difficult to work. Due to its high oil content and hardness, it is very difficult to get a strong and reliable glue joint; though it is an excellent wood for turning on lathe, and finishes well.
4 – Snakewood (Brosimum guianensis)
Offering a hardness of 3,800 lbf (16,900 N), the snakewood is an excellent wood not just because the material is hard but also because of its beautiful and unique pattern.
Just as its name suggests, the Snakewood has unique patterns that make it look like the skin of a snake.
But it is extremely rare, this wood is very expensive and not practical for use in building homes. It’s actually considered to be among the most expensive woods in the world!
Snakewood is known for its snakeskin pattern characteristics. Wood is typically a reddish brown, with contrasting darker brown or black patches. Color tends to darken and homogenize with age and exposure; has typically straight grain, with a fine even texture and high natural luster; very durable and also resistant to insect attack, though it seldom used in exterior applications where durability would be an issue. Snakewood also shares many of the same working properties with Bloodwood which is extremely dense, and has a pronounced blunting effect on cutters; tends to be quite brittle and can splinter easily while being worked. Despite having working difficulties, it turns well and finishes to a high polish.
3 – Gidgee (Acacia cambagei)
This member of the Acacia family is endemic only in Australia. The Aussies are lucky to get their hands on this wood as it has a hardness of 4,270 lbf (18,990 N).
With its dark coloring, the Gidgee is often used as a substitute for ebony. Builders who used this material know it’s harder than the original.
Gidgee has a medium to dark reddish brown heartwood, sometimes with darker streaks; has yellowish sharply demarcated sapwood. Curly figuring is also seen on some pieces, and is called “ringed gidgee.”
2 – Lignum Vitae (Guaiacum officinale)
Best known as the ‘hardest wood in the world’, the Lignum Vitae has a hardness of 4,390 lbf (19,510 N).
It is actually such an excellent and popular building material that it has now been listed under the Convention on International Trade of Endangered Species (CITES) as an endangered species.
Trade of wood listed under CITES is restricted. Lignum Vitae is listed under Appendix II.
CITES Appendix II – This appendix contains species that are at risk in the wild, but not necessarily threatened with extinction. Species in this appendix are closely regulated but are typically not as restricted as Appendix I.
Though the species is not as closely regulated as those in Appendix I, restrictions for this wood also includes finished wood products.
This means that the sale of these items is prohibited unless you can provide proof that this was built before the listing date – and it’s 2/13/2003 for Lignum Vitae.
But even if you have evidence that the object was built before this date, it is still illegal to take the finished product you bought across international borders, unless you have a proper export permit.
Lignum Vitae have olive to a dark greenish brown to almost black heartwood, which sometimes with a reddish hue. The color tends to darken with age, especially upon exposure to light; has interlocked grain, sometimes severely so; a very fine texture and an oily feel. The bare wood can be polished to a very fine luster due to its high natural oil content. Lignum Vitae is a very durable for outdoor use and is also very resistant to insect attack.
1 – Quebracho (Schinopsis spp.)
Known as the hardest and heaviest wood in the world, the Quebracho got its name from the Spanish term quebrar hacha – and that means ‘axe breaker’.
With a hardness of 4,570 lbf (20,340 N) it really lives up to its name.
Quebracho has a light to medium reddish brown heartwood which sometimes with darker blackish streaks. The color darkens upon prolonged exposure to light; has pale yellowish sapwood which is distinct from heartwood, though the transition is gradual; has fine, uniform texture with a high natural luster. The wood grain tends to be irregular, ropey, and interlocked. The wood is rated as very durable, and is also resistant to insect attacks which also have excellent weathering characteristics. It is known to be difficult to work on account of its density and irregular grain; has high cutting resistance, as well as pronounced blunting effect on cutters. Dries slowly—and tends to crack, check, and warp while drying. Turns and finishes well, and also able to take on a high natural polish without any finishing agents.
(Source: Eric Meier of Wood Database | Janka Scale Rating)
