Posted 15 June 2012 - 03:08 AM
The metal in which the setting is built is completely irrelevant to fluorescence. The only reasons for looking at fluorescence at all are:
1. If you are bothered by the appearance of the diamond under UV light. Not everybody wants to have a blue (or yellow, green etc.) star blazing on their finger, but then not everybody goes to a tanning salon or a disco with "black lights" wearing a diamond, and these are the only places where you'd have the effect.
2. If the fluorescence causes an oily or hazy appearance under natural light. This is quite rare but it does happen. However it is highly visible, and only manifest in stones with strong/very strong/extremely strong fluorescence.
3. If the fluorescence colour is undesirable - e.g. yellow fluorescence in a colourless diamond. This may cause the appearance of the diamond to change under natural light - however it is only apparent in stones with strong fluorescence and above.
By "fiddle" I assume you mean "girdle". Perhaps thinking about it like this may help:
a. Too thick ("Thick" and above): you are paying for weight that does not add to the appearance of the diamond.
b. Too thin ("Very Thin" and below): there may be a danger of breaking the stone while setting or wearing the diamond.
c. Too variable (more than three grades): see above, plus the risk that the cut is asymmetrical and not producing a good looking stone.
Ultimately, though, these are only guidelines, because the report does not contain enough information to determine whether many of the potential problems exist in reality. For example, you could have a girdle that is medium across the whole diamond except in two points (less than 5% of the girdle) where it is XTK and XTN. Is it a problem? No. But it looks "bad" on the report.