Jack Valmadonna Lunzer (1924–2016) was an industrial diamond merchant and the custodian of the Valmadonna Trust Library. He was born in Antwerp in 1924, where his British father was working as a diamond dealer for De Beers. He was a great-grandson of the scholar Eliezer Liepman Philip Prins (1835-1915). His grandfather, Julius, was the founding president of the in London. He moved to London as a child where he was educated. He worked during World War II in a Spitfire engine factory making diamond tools. He began to work under his father but disliked working for De Beers, so he established his own firm, Industrial Diamond Company, exploiting the niche market for industrial diamonds. He took over his father's dealer business in 1949 and later expanded into mining. By the 1980s, his company