It is not only enhances the beauty of the eyes, but can be used for its medicinal benefits too. It is a greyish black coloured shiny stone which is rubbed on the hard surface like stone or a tile. It is obtained from the rock which is situated in Saudi Arabia. It is a greyish black coloured shiny stone which is rubbed on the hard surface like stone or a tile. It is obtained from the rock which is situated in Saudi Arabia. Itis called as Kohal in Tibb-Unani Medicine. Kohal is the sufoof (fine powder), which is applied on the eyes or to the inner surface of the eye lid, with the help of a thin stick or either mixed with water or oil for the base. Kohal is the finest powder form of the medicinal preparation used externally to strengthen the eyesight and to cure other eye aliments.