Born at Devonport, Plymouth (6 September 1807), Hunt's father was a naval officer who drowned while Robert was a youth. Robert began to study in London for the medical profession, but ill-health caused him to return to settle in Cornwall.

In 1829 he published The Mount's Bay; a descriptive poem ... and other pieces but received little critical or financial success. In 1840 he became Secretary to the Royal Cornwall Polytechnic Society at Falmouth and was brought into contact with Robert Were Fox, with whom he made investigations into the early physics and chemistry of photography. 

Hunt took up photography with great zeal following Daguerre's discovery, and developed the actinograph, introducing business processes.  Such devices were developed and described by Hunt, in 1845, as an improvement on T B Jordan's 1839 Heliograph.

Hunt's Manual of Photography (1841, fifth edition 1857) was the first English treatise on the subject. Hunt also experimented generally on the action of light, and published Researches on Light in 1844.  In 1845 he accepted the invitation of Sir Henry de la Beche to become Keeper of Mining Records at the Museum of Economic (afterwards Practical) Geology, and when the School of Mines was established in 1851 he lectured for two years on Mechanical Science, and afterwards for a short time on Experimental Physics.

He was elected a Fellow of the Royal Statistical Society in 1855. In 1858 he founded, with the Royal Cornwall Polytechnic Society, The Miners Association. His principal work was the collection and editing of the Mineral Statistics of the United Kingdom, and this he continued to do till his retirement (1883), when the Mining Record Office was transferred to the Home Office. He was elected fellow of the Royal Society in 1854, and in 1884 published a large volume on British Mining in which the subject was dealt with very fully, from an historical as well as a practical point of view. He also edited the fifth and some later editions of Ure's Dictionary of Arts, Mines and Manufactures. He died in London on 17 October 1887.  

A Mineralogical Museum at Redruth Mining School was established in his memory.  This closed in 1950, and the minerals were transferred to the School of Metalliferous Mining - now the Camborne School of Mines. He also collected and wrote Popular Romances of the West of England (1865), which included a record of myths and legends of old Cornwall, and proved so popular that it went through a number of editions.