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)

The war
When Munich made it clear that war must inevitably come, Payne joined the Territorial Army and was trained as a gunner, whilst I enrolled with the Auxiliary Fire Service in London. When war was declared Payne was called up at once and spent the next few years fighting with the Eighth Army, rejoining the laboratory in September, 1945, just in time to prevent my being totally submerged in a sea of pearl testing. I was able to carry on with such testing work as there was with the aid of Sgt Stelling, a stalwart commissionaire, who had been taken on for the holiday period but who stayed for the ‘duration’. Actually, after the initial shock of war and the London ‘blitz’, the amount of testing work became quite heavy for one person. The number of tests undertaken dropped from the 1938 figure of 776 to 531 in 1939 and 323 in 1940, but had risen to 782 in 1944 and to 1062 in 1945. It was in 1946 that the really great expansion began and we enlisted the help of Robert Webster and Alec Farn, which completed the ‘Phalanx of Four’ which coped with the strenuous testing work of the next 25 years.

I mustn’t dwell on those war years, as I want to carry on with the story of discovery of new gem minerals, but a few points perhaps may be worth recalling.

As a safety precaution, our committee had moved our valuable X-ray equipment to a basement belonging to Johnson, Matthey & Co in Poland Street. This made the testing of undrilled and part-drilled pearls a very time consuming business, as I had to go down to Poland Street to take the photographs, and then post back to the laboratory to develop them.

The laboratory had several ‘near misses’ with bombs and fire, with minor damage. On the worst occasion I was luckily fighting a fire nearby and obtained permission to see how things were in the lab. A large cupboard full of chemicals had fallen on its face, making a truly unwholeseome mess on the floor. All I could do at the time was to pick up the small bottle containing the spontaneously inflammable yellow phosphorus, which I could see glowing in the dark, and put it into a bucket of water to wait for the morrow. I also had to comfort as best I could our diminutive housekeeper and his tearful wife, who had been sleeping each under one of our endoscopes when the bomb fell, and awoke to find that the apparatus had fallen on and around their legs. It required a good deal of cannibalization from other endoscopes to get ours into working order again.

During this war period I was able to do some useful work on the classification of diamond absorption and fluorescence, the distinction between pyrope and red spinel, etc. I also became aware for the first time of the advantages of the Becke 2458 prism spectroscope for spotting purposes, and with its aid discovered the ‘difficult’ absorption spectrum of turquoise, which has
since proved extremely useful. But now I must resume my main narrative.

Taaffeite
The discovery of the new gem mineral Taaffeite reads like a gemological fairy tale. Count Taaffe, only son of the 12th Viscount Taaffe of Corran, Baron of Ballymote in County Sligo, Ireland, was born in Bohemia in 1898, and died in Dublin in 1967. He was the first of his family to be allowed to return to Ireland after its long exile in Bohemia and Austria. Taaffe was a keen amateur both of gemology and astronomy, and found it both profitable and interesting to peddle in gemstones. Amongst his sources for inexpensive stones were the boxes of addments which jewelers keep behind their counters, finding them useful for jobbing purposes. In October 1945 he spent some days looking through the boxes belong to a friendly jeweler, Mr Robert Dobbie, and paid him £14 for the stones which interested him, which were mostly broken out of jewelry: badly rubbed or chipped in many cases.

Taffee worked with meager equipment, but made very effective use of what he did possess. He had no refractometer and no accurate balance. His chief instrument was a Bausch and Lomb binocular microscope without a stage, giving a magnification of 21 diameters.

His first steps, to which he attached great importance, in tackling a mixed batch of stones such as the lot from Mr Dobbie, was to clean the stones very thoroughly and then divide them by eye into batches according to color. He then examined each stone very carefully, holding it in tongs an scrutinizing it from all angles over a sheet of white paper. The illumination was a flexible desk lamp with a 100 watt bulb.

The stone which, incredibly, was later found to belong to a new mineral species was amongst a group of violet, mauve, and lilac colored stones. These were mostly spinels, but the stone in question showed in certain directions distinct signs of double refraction. In his words, ‘every speck of dust on the back and every scratch appeared double, like on a badly wobbled snapshot’. Since, as we now know, the stone had a D.R of only 0.005 and weighed only 1.42 carats, this was a remarkably acute piece of observation. He confirmed that the stone was birefringent by a test between crossed nicols, took a remarkably good density measurement (the average of ten attempts, using a hand-held balance) and finally on November 1st he posted the stone to me at the laboratory with a covering letter: ‘This time a new riddle: what is this mauve stone? It seems to me to answer all the characteristics of spinel, yet it shows double refraction: doubling of facets visible under the Greenough, extinction when polarized, though with queer color effects. Could anomalous double refraction be so strong? R.I too high for topaz, too low for corundum. What is it?’

The stone as received weighed 1.419 carats. Its shape suggested that it had been cut in Ceylon. The refractive indices were 1.718 for the extraordinary ray and 1.723 for the ordinary ray—thus the stone was uniaxial negative. It gave a clear uniaxial interference figure through the table facet. The density as then determined by hydrostatic weighing in ethylene dibromide was 3.621—later corrected to 3.613 by our Clerici solution flotation method, using blue spinels as indicators, one slightly denser and the other a little less dense than the taaffeite. The absorption spectrum was weak, but resembled that of blue spinel very closely.

I replied to Count Taaffe on November 5th, stating our findings and asking permission to have an X-ray analysis made if possible without harming the stone.

Preliminary X-ray tests carried out by Dr Claringbull confirmed the optical indications that the stone could not be spinel. To enable more X-ray and chemical work to be carried out Count Taaffe courageously agreed to having first one slice and then another removed from the culet region, stipulating only that the remains of his historic little stone be returned to him as a faceted gem. This work most skillfully carried out by Charles Mathews Lapidaries Ltd, the stone being reduced first to 0.95 and then to 0.56 carat. With a little imagination one can appreciate Taaffe’s feelings, knowing that he had discovered something quite new to science, but with only one small specimen as the representative of the new species.

On small crushed fragments from the stone X-ray powder, rotation and oriented Laue photographs were taken, showing the mineral to be hexagonal and to belong to the hexagonal trapezohedral class of symmetry—a class to which only ‘high’ quartz (formed above 573ºC) is known to belong. Preliminary analysis showed the presence of magnesium, alumunium and beryllium, and the final analysis, which was not completed until 1951, and was carried out by Dr Hey on only 6.16 milligrams of material, gave the essential formula as MgO.BeO.2Al2O3—that is, intermediate in composition between spinel and chrysoberyl. The ‘Oscars’ were mounting up for taaffeite: it belonged to a very rare class of crystal symmetry; and it was the only mineral known to contain both beryllium and magnesium as essential constituents. Data for an artificial compound of similar composition which were published in 1946 showed only a rough resemblance to those for taaffeite.

Naturally we kept a sharp lookout for further specimens, and examined every pale mauve spinel we could lay our hands on with extreme care, but it was not until October 1949 that the second taaffeite came to light, the honor and credit falling to C J Payne. He was working rather late in the laboratory on an interesting collection of 104 stones (mostly from Ceylon) sent in by a dealer for a routine test. There were a number of green sapphires and pale blue spinels and one kornerupine, which served as a curtain-raiser for a pale mauve stone weighing 0.86 carat which gave what appeared to be a taaffeite reading on the refractrometer. This was confirmed by the observation of a uniaxial interference figure. Payne was naturally enormously excited by his discovery after four years of searching, and rang me up at Goldsmith’s Hall where Webster and I were attending at a Gemological Exhibition being held there. Next day I was on holiday in Devon and had to carry on some cautious haggling by telephone with Payne as intermediary. At any cost, we had to have that stone. By using the kornerupine as a stalking horse we were able to obtain the two stones for £20.

After publication of the taaffeite story in Nature, the gemological journals, and Mineralogical Magazine in 1951, keen gemologists the world over were on the lookout for further specimens, but taaffeite number three did not appear until Christmas Eve, 1957, when it was spotted in the New York Gem Laboratory by our friend Robert Crowningshield. A further ten years were to elapse before a fourth specimen was identified in America following an article on the subject by George Bruce in the Modern Jeweler. This was a ‘giant’ of 5.34 carats, and, surprisingly, dark brownish purple in color.

In 1963 came a report that crystals of the mineral up to 1cm in length had been found in the Hunnan Province of China, though not of gem quality, and specimens are to be seen in the Mineralogical Museum of the Academy of Sciences in Moscow. Since then, tiny green crystals found in the Musgrave Ranges of Central Australia were found to be a ‘polytype’ of taaffeite in which nine subcells instead of four make up the unit cell, giving threefold in place of sixfold symmetry to X-ray patterns. One day, I am sure, a pebble of taaffeite will be found in the Ceylon gem gravels.

Of the four cut taaffeites mentioned, the original specimen was purchased by Mr R K Mitchell after Taaffe’s death, together with other stones from his small collection; the stone discovered by Payne is where it should be—in the Natural History Museum in South Kensington—while the American stones are apparently both in the hands of a private collector, though one was on show for a year at the Smithsonian Institute in Washington.

(continued)