THE AUSTRALIAN GEMMOLOGIST | An Interesting Pair of Earrings
An Interesting Pair of Earrings

Figure 1. A pair of earrings, length about 3.5 cm. Earring 1 on left, earring 2 on right. Photo courtesy of Léonie Rennie.
At one of the monthly meetings of Western Australia’s Gem Appreciation Group, a member brought along a particularly fascinating pair of earrings that had been made in Thailand. These are shown in Figure 1. Each earring measured about 3.5 cm in length and comprised a large mauve cabochon and a smaller, creamy-gold coloured cabochon, with each of these partially surrounded by pink transparent stones. The owner had been told the mauve stone was jade. The other opaque stone was pearl shell, with the flat under surface clearly revealing mother of pearl, suggesting mabé pearl. The pink stones were a mix of faceted round, oval and marquise shapes with one square stone on each earring. The stones were fairly well-matched in colour and the owner was advised they were pink sapphires.
Due to the large variety of specimens brought by members that day we didn’t have a great deal of time to examine the earrings, but the pearl was easily identified and we thought the larger cabochon could be jade, possibly dyed mauve. The pink stones needed closer inspection, but one member put the earrings under the UV light source and the results were very surprising. In Figure 2 we see the two earrings, side by side under long-wave ultraviolet (LWUV) light, and Figure 3 shows the fluorescence of the earrings under short-wave ultraviolet (SWUV) light. The photos indicate no fluorescence from the mauve jade, as would be expected from a natural rather than a dyed stone. The pearl fluoresces a similar blue colour under both LWUV and SWUV. The pink stones are all bright crimson red under LWUV, but a mixture of paler pink, or a slightly bluish white under SWUV. Both natural pink sapphires and pink spinels fluoresce crimson under LWUV, and weaker under SWUV. But bluish white? Could they be sapphire? Some synthetic spinel can fluoresce a bluish colour under SWUV light. We asked the member to bring the earrings back to the next meeting so we could make a detailed examination.
At further meetings, we were able to spend more time examining the earrings closely. We confirmed that the mauve cabochons were indeed natural lavender jadeite and the other cabochons were good quality mabé pearl. We spent a lot of time with the pink stones surrounding the cabochons!
The earrings have a metal frame the colour of silver; it is a cast setting without any claws. The shape of the earrings made it impossible to use a refractometer to find a refractive index on any of the pink stones without removing them from the setting. Of course, that also meant that determination of specific gravity was not possible. Fortunately, the microscope and polariscope gave informative results.
Many of the pink stones in both earrings showed undulating dark bands under the polariscope, that looked similar to the anomalous double refraction shown by some synthetic spinel. No less than 12 of the 22 pink stones showed bright rainbow colours, and careful inspection with the addition of the conoscope revealed a uniaxial optical figure. Further, when those stones that did not produce a uniaxial optical figure were observed at a different angle they were clearly birefringent. Any thought that the dark bands might be the undulating anomalous double refraction shown by synthetic spinels was quickly cast aside and spinel was discounted completely. The next step was to determine whether the stones were natural or synthetic.
We turned to the microscope, and found that many of the stones contained veils that appeared to be healed fractures, or fingerprints, or inclusions, and sometimes, both veils and inclusions. Given the pattern of fluorescence, the uniaxial figures and the inclusions, most of the stones appeared to be natural sapphires. But what about the five stones showing bluish white under SWUV? All of these gave uniaxial figures on the polariscope, and three had a veil, or fingerprint inclusions and one had a veil and inclusions. Figure 4 shows a view under the microscope of one of the pink stones that fluoresced white under SWUV. The photo was taken from the back of earring 2, of the oval stone next to a square stone. We found little evidence to convince us that the stones had been heat-treated.
We agreed that all of the pink stones were natural sapphires, but how could we explain the difference in fluorescence? The three stones on each earring that fluoresced either pale bluish white or a much paler pink were in matching positions. Further, they were the larger marquise or oval shaped stones, so perhaps these six stones were drawn from a different pool of facetted stones that were obtained from a different geological source. This could account for slightly different chemistry that was affecting fluorescence.
Our conclusion was that these were unusual and attractive earrings, containing stones that were lavender jadeite, mabé pearl, and natural pink sapphires from a mix of locations.

Figure 2.
A. Earring 1 under LWUV.
B. Earring 2 under LWUV.
Photos courtesy of Léonie Rennie.

Figure 3.
A. Earring 1 under SWUV.
B. Earring 2 under SWUV.
Photos courtesy of Léonie Rennie.

Figure 4. This sapphire is host to healed fractures, and flat films viewed at such an angle (incident light totally reflected) that they appear almost black. Field of view 4.5mm.
Photo courtesy of Francine Payette.