The Janka Rating scale measures the hardness of different timbers. However, like many things that appear to be simple, the scale becomes complicated because different countries apply different systems. For example, in many European countries, the rating is done on a metric basis (kilogram-force), but the Imperial system of 'pounds force' is used in the USA. The rating is derived from the force required to embed a steel ball in the wood. While the actual amount of force needed is of little interest to a furniture customer, the comparative hardness with other woods is a helpful guide. For example, Black Walnut has a reading of 1010 on the Janka Scale. Teak is just below that at 1000. Mahogany varies around 800 depending on the species, while Iroko is much harder at 1260. Afromosia is the hardest of all the woods we have covered at 1570.