Absolutes cannot be considered true essential oils, because they are not obtained from steam distillation. There are some plant oils that cannot sustain high temperatures and pressure and still maintain all their natural healing properties. For this reason, chemical solvents are used to extract the oily substances. Ethanol, methanol, benzene, and hexane are popular solvents to use, though only ethanol is non-toxic.
Absolutes contain more molecules of different sizes than most essential oils do. Even fatty oils are found sometimes.
Examples of absolutes are Jasmine, Neroli, Tolu or Peruvian Balsam, and Onycha, which is an oil used in the Bible. Tincture of benzoin is made from the same plant that Onycha comes from.
Citrus “essential” oils are part of a group called expressed oils. Technically these are not essential oils either, because they don’t come from steam distillation of plant material. Actually, these oils are pressed from the fruit rinds much like olive oil is pressed. Expressed oils can contain some larger molecules, and do not contain any artifacts since there is no heat involved.