Large pear shaped paraiba type cyan colored tourmaline#941

large, paraiba type, cyan color, pear shaped tourmaline gem beautiful, large, cuprian tourmaline from Mozambique that has the classic cyan color and is flawless.

This is one of the most important gemstones in the collection. It weighs 13.90 carats and is the only pear shaped stone in the collection. A friend of mine designed the cut to maximize the yield from the rough and the optical properties of the finished gemstone. The rough was deeply water worn as is all rough from Mavuco Mozambique. It was unusual because the rough was flawless and uniformly stained by iron. The staining caused the rough to look greenish rather than the more desirable cyan blue.

The finished gemstone is flawless, has a good visual impact (neon brightness) and a fine polish. The only problems I generally have with cuprian tourmaline from Mozambique is under cutting during polishing on facets perpendicular to the principle axis. The cut has more flash in the pointed area of the gem, which is expected in a pear shaped gemstone.

I have tested the gemstone with my spectrometer and found the characteristic twin absorption peaks in the infrared of copper. I also have a nice picture of the gemstone along with its absorption peak from a commercial laboratory that I will attach to the bottom of this post.

This was my greatest bet on a single piece of tourmaline rough and I won with a large clean cyan gemstone with a nice neon glow from copper.

The twin peaks of absorption in the following graph that show the gemstone contains copper are at about 700 and 900 nm.  Iron in tourmaline can produce an identical, cyan color, but it only has the 700 nm peak.  The 900 nm absorption peak is outside the visible light range and therefore can not effect color.

Bruce

Mozambique Cuprian Tourmaline Spectra

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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