• Boswellia sacra (aka B. carteri or B. thurifera)

This is the Arabian Frankincense, and the best quality comes from the Oman and the Yemen. According to western buyers, the highest grades are known as Silver and Hojari. Although the Omani's themselves generally consider Silver to be a better grade than Hojari, most Western connoisseurs think that it should be the other way round. This may be due to climactic conditions with the Hojari smelling best in the relatively cold, damp climate of the Europe and North America, whereas Silver may well be more suited to the hot dry conditions of Arabia. This information, however, is obtained largely from dealers, and there are notable inconsistencies amongst differing sources.Local market information in Oman suggests that the term Hojari encompasses a broad range of high-end frankincense including Silver. Resin value is determined not only by fragrance but also by color and clump size, with lighter color and larger clumps being more highly prized. The most valuable Hojari frankincense locally available in Oman is even more expensive than Somalia's Maydi frankincense derived from B. frereana (see below). The vast majority of this ultra-high-end B. sacra frankincense is purchased by His Majesty Sultan Qaboos bin Said the ruler of Oman, and is notoriously difficult for western buyers to correctly identify and purchase.Some literature identifies B. sacra as growing in Oman and Yemen, and B. carterii as growing in Somalia. The latest scientific opinion is that these are both the same species and should correctly be called B. sacra. Growing conditions vary significantly, however, affecting both tree development and resin produced. Trees in the narrow fog-laden zone where the desert meets Oman's southern mountain range, a region known as the Nejd, grow extremely slowly and produce very high quality resin in large, white clumps. Not surprisingly, Omanis and other Gulf State Arabs consider this to be superior to all other resins produced in North and Northeast Africa, India, and Asia, and it is priced accordingly.

• Boswellia frereana

This only grows in Northern Somalia where the locals call it "Maydi", the king of all frankincense. In the West it is called "Coptic Frankincense" as this is the type and grade used by the Coptic Church of Egypt. It is virtually unobtainable outside Arab counties as 80% of production is sold to Saudi Arabia where it is traditionally brought home by Muslim pilgrims. The remaining 20% is sold to all the other Arab counties put together. The most expensive Omani B. sacra is sometimes sold interchangeably with B. frereana, although the smell is very different.

• Boswellia serrata

This is the Indian frankincense. Its aroma is generally considered to be far inferior compared to B. sacra or B. frereana.

• Boswellia papyrifera

This is a superior version from Ethiopia, but is virtually unobtainable in the West. Anyone interested in frankincense would be well advised to first obtain a small sample of each type from a reputable dealer in order to ascertain the difference between each resin.

• Medicinal Uses