Gemscentric

Written by Julian Robov


Fifty Six


She was reading the Bangkok Post and Nation, as Manuel arrived. He had already prepared the test stones for a second and final trial. After thirty minutes, Rudy and James entered, apologizing for being late. They watched nervously, as Manuel placed the ten test stones on the desk. She was provided with a loupe, tweezer, cleaning cloth, polariscope, dichroscope, refractometer, microscope, spectroscope, heavy liquids and a fluorescence kit. A few text books related to gem identification were also available as reference. And finally, she had two hours to identify ten blue gem materials. Jambo paused.

Weight: 2.95 carat, oval

She cleaned the stone first and after visual observation, she decided to go straight to checking its refractive index. It was 1.762-1.770. Then she proceeded to the microscope. Under magnification, she saw tiny crystals, long needles, liquid fingerprints, color patches and three-phase inclusions confirming the gem as natural. Spectroscope examination revealed strong bands at 450 and 460nm, and a separate narrow line at approximately 470nm. She decided to skip the polariscope, dichroscope, heavy liquids and fluorescence test. Finally, the blue gem was identified as natural untreated blue sapphire.

Weight: 3.50 carat, oval

After routine visual observation, she checked the refractive index. It was 1.762-1.770. Under magnification she observed exploded crystals, dissolved silk, feathers, uneven color patches and two-phase inclusions. Spectroscope examination revealed only 450nm line. She identified the blue gem as natural heat-treated blue sapphire.

Weight: 4.00 carat, cushion

The blue gem had a good color. After cleaning, she checked the refractive index. It was 1.762-1770. Microscope examination showed gas bubbles, curved striae and curved color banding. The two tests confirmed the blue gem as synthetic flame-fusion blue sapphire.

Weight: 4.55 carat, oval

After cleaning the stone, she observed with a loupe its luster. Something was not right. The refractive index was consistent with 1.762-1770 reading. With magnification the stone revealed color bleeding at facet junctions and girdle plane. Fingerprints and some tiny-looking crystals were also present. With the help of an immersion cell, she saw the tell-tale signs better. Finally, the blue gem was identified as surface diffusion-treated blue sapphire.

Weight: 5.01 carat, oval

The stone was deep blue. After cleaning, she studied its personality. The brilliance flashes were good. The refractive index was 1.762-1.770. Magnification showed the stone was a doublet. There was a difference in the luster. The crown part revealed long needle-like inclusions with tiny crystals, while the pavilion part showed curved color banding and gas bubbles. Finally, the blue gem material was identified as a corundum-doublet—with top as colorless natural sapphire, and base with synthetic flame-fusion blue sapphire.


Weight: 5.45 carat, oval

The color looked deceptive. Visual observation revealed the luster quite similar to the previous stones. The refractive index was 1.762-1770. Magnification revealed gas bubbles, curved striae with color bleeding at facet junctions and girdle plane. This was very unusual. Spectroscope examination was difficult. Finally, she concluded the blue material as surface diffusion-treated synthetic flame-fusion blue sapphire.

Weight: 6.02 carat, oval

After cleaning the stone well, she checked the refractive index. It was 1.762-1770. Under magnification, she saw metallic particles, flux fingerprints, and flux crystals. The pattern looked very similar to natural inclusions, but there was a difference in its texture. Finally, she identified the blue gem material as synthetic flux blue sapphire.

Weight: 6.70 carat, oval

Although the stone resembled a blue sapphire, there was something different. Dichroscope observation confirmed the stone was trichroic showing blue, red, and greenish yellow. The refractive index was 1.691-1.704. Magnification wasn’t helpful. Only a few tiny crystals and fingerprint were present. She decided to skip other tests. She identified the gem material as blue zoisite (tanzanite).

Weight: 3.00 carat, oval

After cleaning, she checked the refractive index of the stone. It was 1.718. The stone was single refractive. Magnification revealed several rows of octahedral crystals, fingerprints and small needle-like inclusions. Without doubt, she identified the blue gem material as natural spinel.

Weight: 7.00 carat, oval

The color was good. With a loupe, she studied the gem. She saw strong doubling of the back facets. There were only a few gems, which showed strong doubling. She knew the stone was double refractive with a high birefringence. Dichroscope observation revealed rich blue in one direction, colorless in the other. Spectroscope showed a distinct absorption line at 653.5nm and a weaker companion line at 659nm. When she did a quick heft test, the stone was heavy—meaning, high specific gravity. Finally, she identified the blue gem material as blue zircon.

It was a tense moment, as Manuel checked the result. She had in fact finished the test in fifty five minutes. Finally, when the result came, Ms Jambo was jubilant. She had identified all the ten blue stones correctly. She had basically relied only on three instruments—refractometer, microscope, and spectroscope. Other instruments were complimentary with the exception of a few stones, such as blue zoisite and blue zircon. She had mastered the skill in a very short time.

She was sipping the guava juice and smiling, as Manuel prepared to leave. His job was over. She thanked him for the excellent presentation and explaining shortcuts for gem identification. Rudy was satisfied with the spectacular progress, and now he was pondering the difficult task of showing the same result during the finale.
As Rudy deliberated with Ms Jambo about the next phase, James called Johnny on his cell-phone. One of Johnny’s brokers, Chai had volunteered to help them out. He was a close friend of Newin, Seri’s trusted broker. They had decided to use Chai as a conduit to persuade Seri to visit Ms Jambo. He could have hardly refused the invitation when she was offering a two million dollar gemstone deal.