Guaiacum officinale, commonly known as roughbark lignum-vitae,<ref name="ITIS">Template:ITIS</ref> guaiacwood or gaïacwood, is a species of tree in the caltrop family, Zygophyllaceae, that is native to the Caribbean and the northern coast of South America.<ref name="GRIN"/>
This small tree is very slow growing, reaching about Template:Convert in height with a trunk diameter of Template:Convert. The tree is essentially evergreen throughout most of its native range. The leaves are compound, Template:Convert in length, and Template:Convert wide. The blue flowers have five petals that yield a bright-yellow-orange fruit with red flesh and black seeds.
Guaiacum officinale is one of two species yielding the true lignum vitae, the other being Guaiacum sanctum. Guaiac, a natural resin extracted from the wood, is a colorless compound that turns blue when placed in contact with substances that have peroxidase activity and then are exposed to hydrogen peroxide. Guaiac cards are impregnated with the resin and are used in determining whether stool contains blood. The heme portion of hemoglobin contains peroxidase and will catalyze the oxidation of guaiaconic acid when hydrogen peroxide is placed on the Guaiac card if blood is present in the stool.<ref>Template:Cite book</ref>
Roughbark lignum-vitae was listed as an endangered species by the IUCN in 1998. It has been overexploited for its valuable wood and medicinal products. International trade of this species is restricted because of its placement in CITES Appendix II.<ref name="IUCN"/> Template:Clear left