From Popular Archaeology in October 2016:
It is mentioned more than twenty times in the Bible, where it is one of the gifts offered by the Three Wise Men. Frankincense (also called olibanum), one of the world's oldest fragrances, is a gum resin that exudes from the bark of Boswellia trees, which grow in countries bordering the Red Sea and the Gulf of Aden. It has been used for more than 6,000 years by every civilization, from Mesopotamia to the present. Regularly burned during religious ceremonies, it contributes to the very particular smell of churches. Despite its long history and the large amount of research dedicated to it, the exact nature of the molecules that give frankincense its distinctive fragrance surprisingly remained unknown.
read entire article here @ Popular Archaeology