Rothman developed a handheld, cylindrically shaped magnifying glass--a device quaintly dubbed a "proportion scope"--that clarifies the pattern of hearts and arrows.

FORBES: Stones on fire

To convince customers they were getting a better rock at a higher price, he developed a handheld, cylindrically shaped magnifying glass that clarifies the pattern of hearts and arrows.

FORBES: Stones on fire

Then he discovered a new Japanese method of cutting diamonds: When viewed under a low-magnification (3x) lens, the stone refracted light in such a way as to give off a pattern of eight heart-shaped sparkles at the bottom of the diamond and eight arrow-shaped fire-bursts through the top--hence the name "hearts-and-arrows" diamonds.

FORBES: Stones on fire