John Parry started his career in the chemical laboratory of Epps, English homeopathic chemists and cocoa manufacturers. Thereafter he worked for a number of years in Leicester. He came to South Africa for health reasons in 1899, working first in Cape Town, but by 1906 he was in the employ of Heynes, Mathew & Co., Kimberley, as a pharmaceutical chemist. As a result of his impressive research the De Beers Company asked him to start its Analytical Department in 1917 and appointed him as chief chemist, a position he held until his death. His analyses of many minerals and rocks from the diamond mines were published in a book by A.F. Williams*, The genesis of the diamond (1932). He also analysed and described two new minerals in the Mineralogical Magazine: 'Afwillite, a new hydrous calcium silicate from Du Toitspan Mine, Kimberley, South Africa' (with F.E. Wright; Vol. 20) and 'On Bultfonteinite, a new fluorine-bearing hydrous calcium silicate from South Africa' (with A.F. Williams and F.E. Wright; 1932, Vol. 23). He also described 'Minerals deposited by bacteria in mine water' (Engineering and Mining Journal, 1923)
Parry became a member of the South African Association for the Advancement of Science in or before 1906, but his membership had lapsed by 1910. He became a member again in 1914, when the association held its annual congress in Kimberley, and served as joint secretary of Section B (which included chemistry) that year and also when the association met in Kimberley again in 1928. He also joined the South African Chemical Institute in 1914.