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Figure 1. The medusa form of this jellyfish (Rhizostoma pulmo) on the left bears a striking resemblance to the gilalite inclusion in quartz on the right. Photos by Francesc Pagès and B. Rondeau (right, magnified 16×).
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More About “Medusa Quartz”
Shortly after the publication of the Gem News International entry on gilalite-bearing quartz (Fall 2005, pp. 271–272), I received a reprint request from a marine biologist who specializes in medusa systematics, Dr. Francesc Pagès of the University of Barcelona. He was surprised by the striking similarity between the gilalite clusters we described and the medusa stage of Rhizostoma pulmo, an attractive but venomous jellyfish he commonly observes in the Mediterranean. Hence, he felt that the name chosen for this new variety of quartz was quite appropriate.
He was also kind enough to send a photograph of a specimen he encountered recently. Placed beside the photomicrograph of a gilalite cluster in “medusa quartz,” the resemblance is striking (figure 1). This provides a surprising and aesthetic link between gemology and marine biology.
Benjamin Rondeau
Muséum National d’Histoire Naturelle, Paris
Chelsea Filters and Synthetic Emeralds
The excellent article on the characterization of Malossi hydrothermal synthetic emerald will be of great value when gemologists start issuing “Country of Origin” certificates for synthetic materials. Unfortunately, today it is of little practical use for the working gemologist.
The authors confirmed what Basel Anderson, the developer of the Chelsea Filter, wrote almost 65 years ago (see Gem Testing for Jewellers, Heywood & Co., London, 1942, p. 56), that is, it can differentiate natural emeralds from green glass, but it cannot separate natural from synthetic emeralds.
On the other hand, the Hanneman-Hodgkinson Synthetic Emerald Filters have been successfully performing this function for almost a decade. I believe the time has come for G&G to acknowledge their existence and in future articles of this nature require the notation of a gem’s appearance through these filters.
W. Wm. Hanneman, Ph.D.
Granbury, Texas
Editors’ Reply
We thank Dr. Hanneman for his comments. Unfortunately, there are some practical limits to the testing we can require from authors, especially if it involves equipment they may not have access to. Note that Gems & Gemology has recognized the utility of the Hanneman-Hodgkinson filters in the past (see E. Boehm, “Portable instruments and tips on practical gemology in the field,” Spring 2002 Gems & Gemology, pp. 14–27), and readers are referred to page 24 of that article for a discussion of their use.
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