Mentha arvensis is the main species of mint used to make natural menthol crystals and natural menthol flakes. This species of mint is grown in India in the state of Uttar Pradesh. (−)-Menthol occurs naturally in peppermint oil (along with a little menthone, the ester menthyl acetate and other compounds), obtained from Mentha x piperita. Mentha (also known as mint, from Greek μίνθα míntha, Linear B mi-ta) is a genus of plants in the family Lamiaceae (mint family). The exact distinction between species is unclear; it is estimated that 13 to 24 species exist. Hybridization occurs naturally where some species range overlap.