The diamond cut was 13 1/2 carats, worth $10,000. It was cut by Lazare Kaplan, who had cut the famous Jonker diamond. He was assisted by his son George, who explained each step of the process.
First the stone and another sharp-cutting one were affixed to sticks coated with shellac that held them securely in place. A tiny trench was then made in the diamond to be split. This was done by using the cutting diamond. Later a steel wedge with blunted edge was inserted almost to the depth of the groove.
While the audience held its breath and two attendants the shaky table - Kaplan struck the blow. Done by any other than an expert the gem would have shattered to pieces. The split gem was passed around for all to admire. Four plainclothesmen eyed its progress.
Wiss, a certified gemologist and a member of the board of the Gemological Institute of America, followed the demonstration with a talk.
The exhibition includes many exceptional gems, among them a pear-shaped diamond presented by King Leopold of Belgium to Princess Astrid as an engagement token; a ruby, one of the finest specimens known today; a coffee-colored diamond, and the Jerome B. Wiss Collection of Colored Diamonds.
The most spectacular piece is probably the diamond necklace with an emerald-cut diamond in the center and 61 baguette diamonds.
The exhibition will continue through May 21, from noon to 5:30 P.M., and on Wednesday and Thursday evenings from 7 to 9:30 P.M.
On May 20, at 8 P. M., Kaplan will give another diamond cutting demonstration, and Wiss will lecture.
Three generations of the Wiss family were present yesterday at the Wiss store in Broad street as Mrs. Frederick C. J. Wiss cut a ribbon across the door to mark the story's anniversary. Mrs. Wiss is the widow of a son of Jacob Wiss, who founded the business. About 250 attended the ceremony.