The Pleasures Of Discovery

(via The Journal of Gemmology, Vol.XIV, No.3, July 1974) B W Anderson writes:

(being the substance of a talk given to the Gemmological Association of Great Britain at Goldsmith’s Hall on 29th October, 1973)

Ekanite
For the last of my stones we return to the gem gravels of Ceylon, and once more it was a keen gemologist who set the ball rolling. This was Mr F L D Ekanayake of Colombo, Ceylon, who, in 1953, sent a round cabochon dark green stone showing a faint four-rayed asterism to his friend, Mr R K Mitchell, accompanied by a letter in which he stated ‘I am sure this is a new mineral’. After some preliminary work Mr Mitchell allowed us to try our hand at solving the mystery of this peculiar stone. It appeared to be quite amorphous not only optically but to an X-ray beam, and yet the tiny oriented needles to which the asterism was due argued some degree of crystallinity. The density was 3.28 and R.I 1.60.

An attempt at spectrum analysis in the laboratory showed the presence of calcium, silica, and traces of lead. This last made me think in terms of glass, and I sent the stone to D K Hill, a well-known glass technologist, for his opinion. He at first confirmed the glass hypothesis, but then discovered by a much more skilled spectrum analysis than we could muster, that thorium was a major constituent of the material. Hill’s estimate was about 26 or 27% thorium oxide—which later proved to be almost exactly correct. On hearing this news the penny dropped, and I realized that we are dealing with a metamict—a crystal the structure of which had broken down due to 600 million years or so of internal bombardment with alpha particles, as in the case of the green metamict zircons we already knew so well. The trace of lead was also explained—this was the end product of the disintegration of thorium.

During this prolonged investigation, by another of those extraordinary chances of which I have already spoken, Mr Solomon, who was at the time an instructor of students of gemology in Plymouth, sent me a cabochon stone of this same metamict mineral, asking if I could tell what it was since it had puzzled his students. When I told him the story he kindly gave me the specimen.

As one could expect, Ekanayake’s stone proved to be quite strongly radioactive, leaving a trace after being placed on a photographic film for a few hours. Using a slice taken from the stone, we tried to return it to its original crystalline state by heat treatment: but heating at 1000ºC failed to bring about the hoped for alteration and transformed the stone into an opaque putty-colored mass.

It was several years before the Museum could proceed with the necessary complete analysis, which entailed a formidable piece of work and in the meantime Ekayanake had recovered three further pieces of the mineral from the same gem pit where the original was found—at Eheliyagoda near Ratnapura.

The final analyis, carried out by D I Bothwell, showed the new mineral to be essentially a silicate of thorium and calcium, though about 2% of uranium was also present. A preliminary note was published in Nature on June 10th, 1961, establishing the new mineral at last, and appropriately honoring its discoverer in the name Ekanite. R K Mitchell gave an excellent account of the long drawn out investigation in the Journal of Gemmology, and shortly afterwards Dr Edward Gubelin who, unknown to us, had been working intensively on the new mineral, of which he had acquired no fewer than 12 specimens, published a long and brilliant paper on the subject in Gems and Gemology, The Gemmologist, and elsewhere, which precluded the need for any further work on our part.

Since that time, crystallized forms of ekanite have been reported from Central Asia by Russian workers and from Saint-Hilaire, Quebec Province, in pegmatite veins. The crystals are tetragonal. The reason for these not having been reduced to the metamict stage lies in their much younger geological age—60 million years against 600 million.

One thing that took away much of the pleasure from these investigations into new gem minerals was the long delay between the initial burst of ordinary gemological work on the stones and the final necessary chemical analysis and crystal structure analysis which had to be performed before the mineral could be properly established and the conclusions published a scientific paper. One could not very well press for speed from the skilled Museum workers, for work which involved a great deal of time and effort, which had to be added to their own research programmes and routine work for the department. And we ourselves in the laboratory found it increasingly hard to find time to work continuously on any project as the demands of essential daily testing work became more and more pressing. Visits to the library became lunch-time snatches, and one felt guilty in doing any work which could be termed purely academic. And most of you know how hard it is to pick up the threads of any piece of work which has been put on a shelf and allowed to grow cold.

Amongst the advantages of such pieces of research are the sharpening of technical skills, an increased international reputation for the laboratory and a closer liaison with mineralogists—a liaison which is vital in the present state of our science.

For those of you who have found my topic for this evening too remote from everyday experiences and problems in the trade to interest you, I can promise a thoroughly down-to-earth talk next October, when I understand that I am going to be allowed to speak to you again.