Mastic is a resin used as incense: the pale tears of the mastic shrub of the Mediterranean, chewed as a gum and burned as a light, clear incense; in Western practice it is attributed to Mercury.
Material and correspondence
In the Western system of ritual correspondences it is set under Mercury and the element of Air. Such planetary and elemental attributions belong to the Western esoteric tradition of correspondences, drawn from writers such as Agrippa and codified in the modern period by the Hermetic Order of the Golden Dawn; the material's use as incense is far older and cuts across many cultures. It is described here within that documented tradition of ritual perfume.
An island monopoly and a word for chewing
Commercial mastic comes almost entirely from Pistacia lentiscus var. chia grown on the southern half of the Greek island of Chios, where cultivation of the "tears" has been concentrated for centuries and is now protected as a designated origin product; the practice of chewing the resin, attested since antiquity, gave Greek its verb mastichan, to gnash or grind the teeth, the root that passed through Latin into the English word "masticate" itself. Beyond incense, the resin has a long secondary history as a digestive remedy and, more recently, as a flavoring in Greek and Turkish confectionery and drinks, uses that developed independently of its Mercury-and-Air correspondence in the Western esoteric tables.