Mineralogist and physicist. Born in Humbie (East Lothian), Nicol lectured at the university in Edinburgh. He invented the concept of a thin section which mounted a rock sample on a glass slide and ground it exceptionally thin so that it would transmit light and allow its constituent minerals to be examined. In 1825, he used the double refraction property of a crystal of Iceland Spar to produce polarised light. This he utilised in the Nicol Prism to investigate the optical properties of minerals and other substances. He ground lenses from semi-precious stones and used these to investigate fossilised wood and fluid-filled cavities in crystals.
Unfortunately he did not publish his work until the mid-1820s and this significantly held up the exploitation of his developments.