Dissecting a Dravite Hot Off the Lap.

I am continually amazed by the variety of dynamic colors in tourmaline.  And shifts in color than can make a less desirable color in gemstone still blaze with a unique statement.  And a unique tourmaline certainly gets my attention.

The dravite I just finished was put in line to be cut, because I am low on rough and I try to alternate “exciting” stones with ones that more or less keep me busy.  The well worn pebble had a very rich orangish brown c axis and a rather pale green a/b axis.  Now that sounds interesting with the two colors and the combination could have made a very different emerald cut, but the only practical cut was a round or oval.  It would also have to oriented with the table perpendicular to the c axis to get a reasonable gemstone.  On top of that restriction was the fact that the c axis was so dense that I could not even use all the potential of the rough to make a high yielding cut because the stone would be too dark.  There was at least one good thing about the strong dichroic nature of the rough. (not a great fan of oranges and greens mixing together.) The green would be completely submerged by the orangish brown in the proposed, round because of its pale tone level.

The cutting of the stone was dominated by its fragile nature and the need to sacrifice material to keep the tone level down.  I continued to deliberately reduce the round’s diameter even after I dop the preform and since it is dichroic, I kind of had to guess at the final level of color since I could not see the c axis directly anymore.  I finally stopped grinding it down at about 5 mm because if I can not see its color in that range in size than the stone is pretty much junk.

The polishing turn out to be a very sensitive endeavor.  The removal of material to make meets went fast, but if I put any real pressure on the stone it would mark.  It I tried pressing the issue it would get worse.  So I had to be laid back and let the stone find its own way.  It got so bad with the table that I think the slight increased in weight of my hand on one side of my hand piece caused that side of the table to mark until I deliberately balanced the pressure.  I really began to wonder if I had the patience to finish the table with the quality I strive for in my gemstones.  It was not as if it was on the same order of magnitude as the 10 carat orange amber colored sunset tourmaline I cut years ago.  It was also from East Africa and I think is it similar material.  It also was on of the most difficult tourmalines to polish I have ever finished.  Finally the small table on a less than a one carat stone FINISHED and I celebrated.  The rest of the crown still had its moments, but I had the best of this gemstone.

So how does it look.  I started this post with talking about tourmaline with a differences and that should give you a hint that this little guy is different.  Under incandescent light, which I work under for both light and heat, the stone looks up with a mahogany, brownish orange, flash in a medium dark tone level.  Its change to a paler medium brown with just a hint of green on the edges, when off axis, is the unusual shift.  It is much stronger than I expected and indicates a delicate balance between the forces of red and green in the gemstones make up.  It will have an interesting absorption spectrum with my spectrometer.

So to sum up.  A lot of patience and lost of material has produced a less than one carats gemstone that shifts strongly between a mahogany and  a mild brown all within a medium to medium dark tone level.  A most satisfying effort. (pretty too)

Bruce

Picture to follow

 

 

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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