His father, John Tennant, was an officer in Her Majesty's Customs and Excise; his mother, Eleanor Kitchen, came from a family of yeomen resident at Upton for more than two centuries.

[1] In October 1824, Tennant was apprenticed to John Mawe, a dealer in minerals at 149 Strand in London.

In 1838, on Faraday's recommendation, Tennant was appointed teacher of geological mineralogy at King's College London, later a professor.

[1] Tennant was an earnest advocate of technical education, giving his own money liberally to help, and persuading the Turners' Company, of which he was master in 1874, to offer prizes for excellence in their craft.

[1] Tennant wrote the following books or pamphlets:[1] He also, in conjunction with David Thomas Ansted and Walter Mitchell, contributed Geology, Mineralogy, and Crystallography to Orr's Circle of Sciences in 1855.