Dichroic forest green round#146

A graded forest green round. !48 If you at this standard round brilliant closely you will notice brighter flash than darker flash as you turn it. This because the tonal values, of two very similar colors, are different. This eye clean gemstone is bright and flashy and weighs 2.92 carats.

Face up this standard round brilliant appears to have a nice even medium dark forest green (green with a blue touch), but it is hiding the truth.  When I turned it over to check for inclusions/flaws etc. and rotated it, I could clearly see its tone value change threw the c axis color and the a/b axis color.  So after seeing that this beautiful gemstone is eye clean and with fine crystal, I looked at the gemstone face up again.  As I slowly turned the stone, I realized, as I now expected, that some angles of rotation produce a brighter flash than others.  There was my confirmation of the stone having been cut with its table parallel to the c axis.  I usually can clearly see four slice of pie segments, face up, on stones that are cut that way, but in this case the different colors/tone values mix so seamlessly that a casual look misses the effect.  This neat and mysterious gemstone weighs 2.92 carats.

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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