(Original Forum Question : TO ALL SPECIALIST OF CYPRAEA. HAVE YOU EVERED CHECK YOUR CYPRAEA SPECIMENS WITH THE AID OF A FLOURESCENT LIGHT? I DID. DID YOU NOTICED SMALL SCRATCH MARKS EITHER ON THE DORSUM OR ON THE BASE. THESE SCRATCH MARKS IS TO SMALL TO BE CALLED A SCAR, A DING, AND INFACT, I DOUBT IF THERE IS A TERM FOR THIS AND IS TOTALLY INVISIBLE IF THE SHELLS IS ONE OR TWO FEET AWAY FROM YOUR EYES. THESES MARKS LOOK LIKE NEEDLE MARKS MADE BY SCRATCHING A NEEDLE ON GLASSES. IF THESE MARKS ARE TO NUMEROUS, IT ALWAYS, IF NOT SOMETIMES, AFFECT THE CYPRAEAS SHEEN. I REALLY DON'T KNOW IF THESE ARE JUST NATURAL AND NOT TO BE MINDED IN GRADING CYPRAEA OR ARE FLAWS WHICH IS THE EFFECT IF THE SHELL HAS RUB ON SOMETHING SHARP OR EVEN OTHER CYPRAEA. CAN ANYONE HELP ME? I HAVE MANY CYPRAEA IN MY COLLECTION AND NON OF THEM HAS BEEN GRADED GEM AND A FEW ARE JUST LUCKY TO BE GRADED GEM-/FINE+++. I AM ALREADY HAPPY TO AQUIRE A FINE++ CYPRAEA. ARE THESES MARKS FLAW OR JUST NATURAL? ANYONE?)

These tiny hairline scratches on the nacre can be either from natural or manmade causes. If the shell brushes against coral or falls onto sand or is buffeted by surf-tossed sand, such minute scratches can occur. Sand grains, being largely quartz and similar minerals, are much harder than the surface of the shell. But they can also occur from contact with mildly abrasive surfaces after collecting - sliding the shell across a tabletop, handling it with jewelry on your fingers, or even wiping the shell with a cloth that isn't soft enough or has some fine dirt or grit on it. Remember that the shell grading system is based on ordinary visual inspection - no flaws that can be detected upon close examination with the unaided eye. Special lighting may reveal some minute flaws that may not be seen otherwise; and magnification almost always will. Give me a good 20X microscope and I'll find flaws on any Cypraea, "gem" or not.
(Answer by M. Paul Monfils via the Forum)