Marcel Tolkowsky

{{Short description|Belgian mathematician and gemologist}}

{{Use dmy dates|date=March 2020}}

Marcel Tolkowsky (25 December 1899 – 10 February 1991),{{Cite news |url=https://www.nytimes.com/1991/02/15/obituaries/marcel-tolkowsky-92-a-retired-gemologist.html |title=Marcel Tolkowsky, 92, A Retired Gemologist |work=The New York Times |date=15 February 1991 |accessdate=9 November 2013}} Obituary. an engineer by education, was a Belgian member of a Jewish family of diamond cutters from Poland. He is generally acknowledged as the father of the modern round brilliant diamond cut.{{cite journal |last1=Cowing |first1=Michael |title=Diamond Brilliance: theories, measurement and judgement |journal=Journal of Gemmology |date=October 2000 |volume=27 |issue=4 |pages=209–227 |doi=10.15506/JoG.2000.27.4.209 |url=http://acagemlab.com/Article1/Article1.htm|archive-url=https://web.archive.org/web/20041216230514/http://acagemlab.com/Article1/Article1.htm |archive-date=16 December 2004 }} Many of his family have gone on to become noted diamond cutters, including his cousin Lazare Kaplan and his great-nephew Gabi Tolkowsky.

Tolkowsky, as part of his PhD topic at the University of London, systematically studied the grinding of diamonds.{{cite thesis |first=Marcel |last=Tolkowsky |title=Research on the Abrading, Grinding or Polishing of Diamond, Thesis for the Degree of Doctor of Science (Engineering) |year=1920 |url=http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538936 |type=Ph.D |quote=Note that the thesis does not define the 'Tolkowsky cut', contrary to what is claimed in some third-party references, such as his NY Times obituary.}} Around the same time, in his book Diamond Design, he published the specifications of what would later be called the American Standard (also known as the American Ideal Cut, Tolkowsky cut, and Tolkowsky Brilliant), which is the diamond-cutting benchmark in North America. It was derived from mathematical calculations that considered both brilliance and fire of the stone. Marcel Tolkowsky found that if a diamond was cut too deep or shallow then light would escape out the sides or bottom of the diamond, resulting in a loss of brilliance (white light reflected up through the top of a diamond), fire (colored light reflected from within a diamond), and sparkle (combination of fire and brilliance).{{cite book |title=Diamond Design, A Study of the Reflection and Refraction of Light in a Diamond |date=1919 |first=Marcel |last= Tolkowsky |url=http://www.folds.net/diamond_design/index.html}}

The original model was intended to be a set of general guidelines; several aspects of a diamond's cut had not been accounted for or explored.{{cite web |url=http://www.gia.edu/research-resources/cut-microsite-pdfs/marcel-tolkowsky.pdf |title=What did Marcel Tolkowsky Really Say? |author1=Barak Green |author2=Al Gilbertson |author3=Ilene Reinitz |author4=Mary Johnson |author5=James Shigley |publisher=Gemological Institute of America|date=14 September 2001}} Later modifications of round brilliants differ in minor ways.