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On 11/2/2002 7:05:03 PM
First, let's define the terms for "sparkle":
BRILLIANCE (return of light after being bounced around in the diamond)
SCINTILLATION (return of light which bounces off the outer surface)
DISPERSION (rainbow colors created by the spreading of the white light ray into it's R.O.Y.G.B.I.V. components)
The princess cuts seem to often have good brilliance, but lacking a little in the scintillation department and even more in the dispersion department.
This is usually because of the thinner crowns and wider tables which seem to be common among the princess cuts. Because the crown is thinner, there is less of the "prism length" on the angled facets between the table and girdle. This makes for less "rainbow" flashes.
Then, with a wide table, the surface area of the bezel facets (between the table and girdle) is smaller. This makes for one big "flash" of the table, and correspondingly smaller "flashes" of light from the bezel area facets (scintillation).
This diminishment of dispersion and scintillation is probably what you're noticing, possibly along with a "darkness" which occurs in the center of the princess cut when the pavilion is too deep.
Rich, GG
Sarasota Gemological Laboratory
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Thank you so much for the helpful info..I really appreciate it. Syd