Frankincense (Olibanum) is the crystallized sap of a small tree that grows in the coastal regions of the southern Arabian Peninsula and coastal East Africa. In ancient times, frankincense, like Myrrh, was a precious commodity, sometimes more valuable than gold. Merchants brought this treasure to the great civilization centers of Europe and Western Asia by sea and by a land trail through Yemen and up the Arabian Red Sea coast to the Levant.

Frankincense trees require a limestone-rich soil and are mostly found growing on rocky hillsides and cliffs, or in the dried riverbeds below. The trees grow to about 8m in height (20ft) with branches often beginning near its base. The common Oman, Aden (Yemen), and Somalia species, produce small yellow-white colored flowers with five petals, while the African species produce small pale-red flowers.

Frankincense resin begins as a milky-white sticky liquid that flows from the trunk of the tree The Arabic name is luban, which means white or cream. It's also known as olibanum, and its essential oil is often called "Oil of Lebanon." Frankincense comes in five main colors: white, pale lemon, pale amber, pale green and dark amber. The color of the gum resin is influenced by its harvest time. A whiter gum is collected closer to autumn, whereas a darker color is harvested closer to spring. Frankincense resin from trees growing in the mountainous Dhofar region of Oman is considered the best. The trees also grow in Yemen, Ethiopia, Somalia, Ethiopia, Eritrea, and India.
 

The tool used to scrape the bark of the tree is called a mengaff. The harvester returns to his tree two weeks later to collect the hardened frankincense resin from the tree or from the ground below. Frankincense trees are ideally harvested twice a year, from January to March and again from August to October, with a rest period in between. Collected resins are aged for about twelve weeks. Finer resins are opaque white, semi-translucent white with shades of lemon or light amber.

In ancient Egypt frankincense trees were imported and grown for the gum, which was burned in religious rituals. They used it as a natural insecticide to fumigate wheat silos and repel wheat moths. The resin was a key ingredient for embalming their dead.

Frankincense was one of the precious gifts, of the visiting Magi to the newborn Jesus in the New Testament:
“They presented unto him gifts; gold, and frankincense and myrrh.” (Matthew 2:11).

The tenth-century Persian physician Ibn Sina recommended using frankincense in treatments for tumors, ulcers, vomiting, dysentery and fever, and to relieve nausea. Western herbalists regard frankincense oil as an anti-inflammatory, antiseptic and astringent, and say it is useful as a uterine tonic during pregnancy and labor. It can be chewed as gum and has a mild, pleasant taste and helps to eliminate bad breath.

Charred frankincense has been used to make kohl, the black powder traditionally used by women in the Middle East as eyeliner.

Frankincense today remains an ingredient in various incense mixtures burned in rituals of the Roman Catholic and Orthodox churches.

Researchers have found that burning frankincense indoors improves the acoustic properties of the room.

In 2000, UNESCO inscribed Oman as the “Land of Frankincense”, with the following brief description and Justification for Inscription:

References: http://www.scents-of-earth.com/frankincense1.html; Saudi Aramco World, September/October 2006; http://whc.unesco.org/pg.cfm?cid=31&id_site=1010