Oiled Burmese Star Rubies

Oiled Burmese Star Rubies
By Tay Thye Sun & Loke Hui Ying

Recently, a client brought in three pieces of beautiful oval shape cabochon medium purplish-red Burmese star rubies for examination and its weight range from 3.95, 3.07 and 2.69 carats (Fig. 1).

Fig.1. Three pieces of Burmese star rubies with weight range from 3.95 to 2.69 carats (Photo by Tay)

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The standard gemological testing of the star rubies, R.I. spot reading 1.76, ruby absorption spectrum and UV long wave with strong red and short wave weak red. Under microscopic observation, the rubies showed prismatic arrangement of needle-like inclusions and also arrow head needles (Fig. 2). Besides the needle-like inclusions, some of the fingerprint inclusions show some slightly brownish stain (Fig. 2).

Fig.2. Silk-like inclusions with slight brownish stain along the fine healed fissures (20x) (Photo by Tay)

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Fig.3. Using FTIR, the absorption spectrum of 2850 and 2920 cm-1 indication of some kind of oil in the fissures of this star rubies 3.07 carats (Tay, 2014).

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Further examination using Infrared spectroscopy, the rubies were found to have some kind of oil with the peaks at 2850 and 2920cm-1 (Fig. 3). When this information was revealed to our clients, he said that the Burmese gem cutter would normally dip the polished star rubies in coconut oil after polishing. That explain why the present of oil in fissures.

This call to mind for disclosure of treatment to the gemstones. In 1999, the DATELINE program shown on NBC channel created such a negative impact that lead to the collapse of the demand and also price of emerald in general, so disclosure about oiling of Burmese star rubies should be disclosed.

Reference:
Ruby & sapphire by Richard Hughes.