Pao ferro or pau ferro (Caesalpinia echinata or Machaerium scleroxylum Tul.) is an exotic tree found in Brazil and Bolivia. Its wood is often used for making fingerboards for basses and electric guitars. It has a similar feel and similar tonal attributes to rosewood, but has a slightly lighter colour. The wood may also be used for flooring, fancy furniture, and handgun grips. It is also known by the names morado, palo santos, caviuna, Brazilian ironwood, and Bolivian rosewood, though it is not actually rosewood.
In guitar making, pao ferro is not only used for fingerboards but also can be used for the back and sides of the guitar. Brazilian guitar maker, Giannini, uses the wood in many of its classical guitars. Although similar in many ways to rosewood, pao ferro does have slightly different tonal qualities.
Pao ferro, used as a rosewood substitute, is a strong sensitizer capable of causing acute outbreaks of allergic and irritant dermatitis in workers not previously exposed to it. This, however, has not prevented furniture factories from using the product. Apparently, most workers develop tolerance to the wood. The allergen is (R)-3,4-dimethoxydalbergion, a strong skin sensitizer.