Problems in the Practice

Problems in the Practice

To an inexperienced Gemmologist or a dealer, some of the gems moving around in the market can pose serious problems resulting in a serious financial loss if care is not taken in observation and testing.

1. A blue-green gem was presented for testing with a “Certificate” saying that it was Aquamarine. On examination the following observations were made; Polariscope - unchanged opaqueness; Refractometer – 1.574-1.576; Examination with the microscope revealed swirl marks & air bubbles.

Obviously, whoever examined this gem would have gone by the refractive index. In the first instance, the very small birefringence should not have been the deciding factor. The behavior on the polariscope should have alerted him. Furthermore with the wide prevalence of imitations, synthetics and doublets a microscopic examination are mandatory for all gems. A reexamination of the R.I confirmed that the apparent double refractive reading was not a distinct movement of the shadow edge.

It is advisable to be aware that synthetic gem quality hydrothermal Aquamarine has been detected in the market with typical identifying features such as inhomogeneous growth features.

2. A Sapphire Blue gemstone mounted in a ring and purchased as a Blue Sapphire was presented for confirmation. The colour of the gemstone and the inclusions had convinced the buyer that the stone was indeed a Blue Sapphire. However a simple R.I .measurement proved otherwise. The R.I. was 1.716-1.730.

The closeness of the R.I. to that of Blue Sapphires along with the presence of “ feather-like” inclusions gave it a “look” of Sapphires which obviously misled the owner.

The stone was a Kyanite.

This underscores the importance of having proper gemological confirmation of gemstones whenever a deal takes place.

3. The so-called “Nidana gems” or gems recovered from treasures are proliferating in the market. The owners swear that the gems are more than five centuries old ( assumptions ) and that they have not left their sight. Therefore, it has to be the real thing. One must be careful and test these gems objectively ignoring the claims of the owners. Since of late one sees many carvings of Lord Buddha from Cubic Zirconia, which can prove a bit harder to identify.

4. A word of caution about lots of Alexandrite, which contain colour changing garnets. On the polariscope, you might find anomalous double refraction so all the gems will have to be tested on the refractometer which gives the correct Chrysoberyl R.I`s. There can be cases of Garnets too giving a single reading at around 1.750 so one must always look for the birefringence. After that double check for pleochroism.

5. Recent radio advertisements talk about Golden or Yellow Topazes . If they are indeed being offered along with Amethysts then we should not miss this bargain !! Regrettably even a government institution is selling Golden Quartz as Golden Topaz

Sheriff Abdul Rahuman

Gemmologist, DGemG (Germany ), MGA ( Sri Lanka )

GIA Alumni