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 proportions in a cut??
P:  10/13/2006 9:24:00 PM  
ger100
ger100

Cut Rock
Total Posts: 169
Last Post: 11/20/2009
Member Since: 9/25/2006
 
 		Renee Newman talks about proportions for colored stone cuts. She states that a flat crown will have less sparkle, giving a 3.5:1 ratio for pavillion depth to crown height as ideal. My question: Does this hold the same for all stones? With obviously different RI's among other things, could this make a difference in effect? I just got a purple-blue richly colored (good saturation?) Tanzanite which finally looks pretty decent to me.  It is a trillion, 7.5 x 7.5 (not calibrated), 1.77 ct. It is bluer in daylight and under fluoro, with a slightly more purple tint under incandescent. I believe that this is not AAA, which will be blue under all lighting, or so I've read. There is no central window! Yippee. Only when you turn it, you can see through it on the side angles. My other trillion, the Spessartite doesn't have ANY areas where you can see through the face. Despite a relatively flat crown, the Tanzanite has quite a bit of sparkle, albeit not like the Spessartite. But then the RI of these stones is different, Spessartite is about 1.8, while Tanzanite is slightly lower, about 1.7 (Schumann), AND the Spessartite has a more complex cut, with a lot more facets on the pavillion.

I guess what I'm asking, is, 1) how important are these cut ratios, 2) are they of the same importance for all colored stones, and (if anybody knows), 3) what percentage of Tanzanite is cut by locals who obviously don't know how to get the most out of a stone's properies? (I have bought and returned about 6 Tanzanites)

My own thoughts are that if the Tanzanite had been cut like the Spessartite, it would be a real winner...now a good 2nd runner-up.

Sorry if this is confusing or maybe naive...I am, after all, a newbie.

Also under the dichroscope, I get pinkish, medium and dark purple, and in one small area a bit of turquoise. Could this be an untreated stone?? Book says green or brown mean untreated...???

Thanks!!
Ger
Posted:  10/13/2006 9:24:00 PM

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