Researching a bright blue green round that I just finished cutting.

The rough was expensive and that is understandable when it is glowing blue green tourmaline.  When it arrived I immediately recognized a nice piece of sea foam tourmaline with a medium tone level.  It had a stronger yellower c axis and bluer a/b axis with both axis being centered on green.

I love to blend the colors in sea foam, but the rough had a technical problem.  It was clean enough, so I could work around the minor flaws, if I cut the rough normally.  (But when I chose to make it different, there was some risk involved).  The length of the clipped crystal was really too short for an emerald cut and too long for a standard round brilliant.  Getting a good yeild can be challenge with this in between sized rough.  (The rough was also not deep enough or with a good ratio, for a Barion style cushion, which is an excellent mixer of colors.)  So what I was to do?

I decided to cut the crystal section into a gemstone with its table at 45 degrees to the plane perpendicular to the c axis.   This will produce a uniform color face up, that reveals both colors as you swirl and tilt it.  If it is done right you can squeeze out a little bit better yeild, if the rough has a bit of a flatter crystal side like this one did.  It also relieves me of having to polish a table that would be strongly affected by the c axis.  (A situation that can lead to undercutting during polishing).

Well about a week ago I finish a beautiful standard round brilliant from the rough.  Since I cut the crystal at an angle it did take a significant amount of careful grinding to make the preform, while I got rid of flaws caused by clipping and some surface imperfections.  Still I was reward with a bright glowing uniform blue green round, face up, that shows it bluer side in a swirling dance.

I showed the gemstone to Jeff, the photographer, and he said it approached my high quality cuprian in glow.  Well I had to test that one out for my self.  Testing this comparison is close to my heart, because I contend that high quality cuprian tourmaline in the range of colors from cyan to green (leaving out the blue purples) needs the neon glow to be exception.  That range of Paraiba colors can be duplicated by other chromophores,  (Notably iron) and you can see the effect of this in the definition of Paraiba like tourmaline from the Harmonization committee.

First I compared my new stone with a sea foam that had been cut with its table parallel with the c axis.  It was very close properties to my new round, but you could make out the pie shaped wedges of unblended colors face up.  Then I moved on to my best blue green cuprian gemstone.  The new round was smaller, but both gemstones had similar tone value and color.  Still the cuprian’s neon glow could not be touched.  As a final test I place both stones on the floor in plastic boxes and let the natural light in the room play on their facets.  The cuprian keep flashing while the new sea foam round darkened and went quiet.

There is no doubt that top quality sea foam has a glow about it.  And the glow is a big factor in its desirability and cost.  But it is will never match high quality cuprian tourmaline, with similar tone values and color, in the glow department.

 

Bruce

 

 

 

About Bruce Fry

I was born in Summit, NJ in 1947 and graduated from Summit High School in 1966. I graduated from the Colorado School of Mines in 1970 and after spending another year in graduate school, I left to see the world of Brazil. After spending some more time discovering myself, I ended up working for the Commonwealth of Pennsylvania for 32 years as an Air Quality Engineer in the Department of Environmental Protection. I retired in 2007 and took up faceting gemstones again after a long hiatus that reached back to my twenties. I had started cutting cabochons when I was 13 and bought my first faceting machine when I was 15, but ran out of money and time until I retired.
My great love in gemology is tourmaline and the collection presented here represents my effort to get as much beauty and variety in the colors of tourmaline as I can. I was particularly lucky in being able to get unheated cuprian tourmaline before copper was discovered in gem grade tourmaline from Mozambique.

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