Gemcad Files of Famous Diamonds

GemCad for Windows, created by Robert Strickland, is a computer-aided design (CAD) program for the design of gemstone cutting patterns. It runs under Windows 95 or later on PC compatibles with screen resolution of at least 800 x 600. GemCad simulates a faceting machine and shows you accurate 3-D views of the stone. GemCad understands symmetry, so you typically have to "cut" only a fraction of the facets to get the full design. GemCad can follow paths of light rays through the stone to allow you to optimize a design to minimize light loss. The end product is an accurate faceting diagram that shows several views of the stone with accurate angles, indexes and dimensions. The program has three main purposes:

(1.) Proof-cutting an existing diagram. Proof-cutting a design on the computer allows you to check the accuracy of the diagram and discover pitfalls before wasting valuable rough.

(2.) Editing a diagram. You can take an existing diagram and modify it to optimize its optical performance for different materials. You can scale a diagram to make it fatter or skinnier to fit a certain piece of rough.

(3.) Designing a stone from scratch. Advanced users can use GemCad to create new designs. GemCad frees the user from the tedious calculations required to determine angles.www.gemcad.com. The MS DOS version of the program is free.

Gem facetor Bob Keller has a website with a number of different Gemcad designs, free to download and view.

I added this page to my website because I am frequently asked about Gemcad files of famous diamonds so I thought this would be helpful. I'd like to thank John Franke of Facet Shoppe for his help with putting this page together. :)

The Dresden Green Diamond by Kane. The crown main facets at 4:30 and 7:30 touch into the table facet, creating two facet edges that shouldn't be there.

The Dresden Green Diamond by Elton McCawley. It appeared in the FACETS newsletter in the September 1991 issue. The design is closer to the actual stone than the Kane design but still falls short, and actually more closely resembles the drawing of the Peach Blossom Diamond shown in Herbert Tillander's book Diamond Cuts in Historic Jewelry: 1381 to 1910. Both this stone and the Dresden Green are blocky, antique pear-shaped brilliants, but the Peach Blossom appears to have a less oblong table facet and large, more squarish crown mains at the 10:30 and 1:30 angles.

The Florentine Diamond by Jeff Ford, based on Scott Sucher's design, which was based on Jean Baptiste Tavernier's drawing. Scott originally published his design in the September 2001 issue of Lapidary Journal magazine, as part of a series of famous diamond replica cutting instructions. His design has a slight 'slant' to it. Jeff Ford retroengineered the design into a Gemcad file, minus the slant, to make it easier to cut (hence 'EZ').

The Florentine Diamond by Michael Hing. Based on a drawing from the "Sketchbook" of Thomas Cletscher from the 17th century. The book resides in Boymans-van Beuningen Museum, Rotterdam. The Sancy and Beau Sancy were also featured in the book, drawn accurately. Since they still exist in their original forms, matching the Cletscher drawing, Michael used this as evidence Cletscher's Florentine drawing was accurate as well. It should be noted Scott Sucher is currently retro-engineering a Gemcad file for the Florentine based on the famous B&W photo of the stone, and one Herbert Tillander's drawing, which was also based on the photo. Scott's website: www.museumdiamonds.com Michael Hing has handled a number of historic diamonds and this is in no way meant to be a slander on his character. His reasoning that Cletscher's sketchbook is reliable and sound if you don't take into account the B&W photograph of the Florentine which was taken at a much later date. After all, the sketchbook was created in the 1600s. Furthermore, most people aren't aware of the photograph, or the drawing from the sketchbook.

The Incomparable Diamond, author unknown. The two gray facets on the stone's girdle should be ignored. They are illuminated gray because of a program glitch. The stone's cutting instructions will not call for them.

The Regent Diamond by Michael Hing. The 140-carat Regent Diamond. Michael got the design, originally by Tom R. Barbour, from Datavue but added the missing needle-like facets pointing outward from the culet, the facets that make it a 'stellar brilliant cut'. He also radially split the crown star facets just out from the table and added the culet facet. Tom R. Barbour's replica design left all these out.

Have an accurate famous diamond Gemcad design? Email me at ragemanchoo (at) hotmail.com. I'm always looking for new ones. :)