Guaiacwood, or Bulnesia sarmienti, is a small tree native to South America that yields an oil with a sweet, spicy, smoky, woodsy aroma. The oil is produced by steam distillation of the wood and is semisolid at room temperature but is easily melted with gentle heat and then mixed with alcohol (it's one of the easiest solids to work with and quite pleasant because of the spicy woodsy scent).