Mastiha — mastic gum from a resin tree — is an ancient, uniquely aromatic Greek spice. Greek folk lore has it that only Chias, mastic trees on the island of Chios in the Aegean, shed these aromatic tears. Frank Carollo, at Zingerman's Bakehouse, was inspired to create a very special loaf of bread for us using Chios Mastiha. Made with barley, whole wheat, clover honey, cardamom and mastiha, this bread has a deep texture and a lovely, intriguing aroma. Available in June only. Taste some today.
Wikipedia on Mastic
Greek Travel guide on Mastiha
http://www.greekproducts.com/mastic/