Frankincense is a plant product referred to as a gum-resin. It is a mixture of gum, resin and volatile oil which provides the perfume of such substances and comes in different forms, depending on the species from which it is obtained.
The best quality gum-resin is initially a rather elastic substance which dries hard. It is oily and highly inflammable. Inferior forms are less resilient and break down into a sticky liquid.
The gum-resin is strongly scented, described as woody and balsamic, honeyed but not cloying.
The bark of frankincense trees is rich in resin ducts. When pieces of the outer bark are removed, the resin bleeds out.
In the case of Boswellia sacra, this gum-resin hardens into white blobs called pearls or beads, which are harvested by hand. These may be sold as they are or softened and moulded into a variety of shapes.