In mineralogy, sandarac, or sandarach, may refer to realgar or native arsenic disulphide, but is generally (a use found in Dioscorides) a resin obtained from the small coniferous tree Tetraclinis articulata, native to the northwest of Africa, and especially characteristic of the Atlas mountains. The resin, which is procured as a natural exudation on the stems, and also obtained by making incisions in the bark of the trees, comes into commerce in the form of small round balls or elongated tears, transparent, and having a delicate yellow tinge. It is a little harder than mastic, for which it is sometimes substituted.