A Large, Really Green Round of Mistery#928

Large rich green tourmaline. with a difference. This 19.54 carat round cut with 12 mains on the crown and pavilion doesn't flash much standing still, because it is cut with the c axis at 45 degrees to the table. The rim dances when it moves.

I have just spent a bit of time trying to orient this rich green gem with it c axis.  With a gemstone that weighs 19.54 carats and is distinctly dichroic, that should not be too difficult.  But perhaps I am getting ahead of my story,

When I first saw the piece of rough that was to became this gemstone, I was not impressed with its shape.   It was rated triple A, but the odd shape would limit yield and got me a discount.  The pebble was also completely water worn with not residual indications of crystal facets.  I started out with a round in mind and as I removed the frosted exterior I could easily see the browner green (olive c axis) and the really great bright rich green of the a/b axis.  The c axis had a somewhat higher tone level then the a/b, but its main fault was a lack of transparency and a less desirable color.  I kept wanting to orient the c axis at a 45 degree angle with the table.  This way I would have a round with a face up view that would be a mixture of the a/b and c axis colors and areas of both colors around the girdle.  Thinking about it again, I probably accomplish what I set out to do, but it was probably the most difficult  clean tourmaline I have ever had to preform.

So now what did I get for all my effort.  The standard round brilliant with 12 mains on both the crown and pavilion,  comes in at 19.54 carats.  It has thick crown with  41 degree mains on the pavilion.  Even with a full thickness gemstones, some of the areas of the round fire up quite nicely under moderate light and really show off the a/b color, but the table is pretty much dead.  As I play with the gem by dipping it and rotating it, the rim dances and the denser area under the table opens at steeper angles.  It can be made to dully flash in a very modest way when the gem is close to face up.  What you can see of it, the c axis color dominates under the table.  Now having a dull empty volume under the table is not the greatest, but its lack of response,  keeps the less desirable color of the c axis from dominating the gemstone, while the great a/b color and tone level, dances.  In the real world of distant views and moving gemstone that certainly makes an interesting and pretty gemstone.  It is unique in the collection.

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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