Janka Hardness Scale is a chart that shows the results of the Janka hardness test, which tests the relative hardness of wood. According to the chart, the hardest wood is a tie between Patagonian Rosewood and Redland Rose while the softest wood is Eastern White Pine.
The Janka test measures the force required to embed half the diameter of a .444" steel ball into wood. The scale runs from 0 to 4,000 and the benchmark is Red Oak which sits at a hardness of 1,290. Patagonia Redwood and Redland Rose have a hardness level of 3,840. Eastern White Pine in comparison has a hardness level of 420.