Remember those new samples hopefully awaited at the beginning of this year? (See last month's 'Dust Pearls'.) Then, I put it in writing that there would be news of the ups and down of working with them. It so happens that there have been no ups: the post has not been delivered. There is, however, more to say.
No samples. Therefore no new work. Thus no news. Furthermore, this is as far as my work on pearls is going. I am writing here to draw the line, and this is quite some drawing exercise!
Thanks are due. Then, an academic post mortem ought to be performed, awaiting the final rites—of formal publication.
Foremost, thank you, Pala International, the ultimate gracious host! Blogging for the monthly newsletters kept reminding me that the academic pleasure of digging up natural pearl cores was meant to find something in particular: tell-tale signs of their much sung origin. Not that the practical goal ever stood in the way of a great story:
Back when I started, I could not predict what might be there to see: the latest observations of natural pearl cores were faintly scanned hand drawings published from brilliant, but rough microscopy, around the 1900s. Back then, finding the origin of pearls was drawn by the want of a method for pearl culture. Since, the trail of published work continues around grafting, but not on natural pearl samples. It seemed reasonable to retrace the old steps, and the proposal had resonated: there is a drawer's worth of samples to be grateful for. A scant hundred hours of microscopy allowed skimming through a couple.
As far as I know, still no samples of newly forming natural pearl sacs were described then or since. Back during the quest for a pearl culture method, such observations were sought; then the quest all but disappears. 
Obviously, looking for those emerging natural pearl sacs is tall order; it is not clear what they might look like: for example, might there be some mineralization, perhaps similar to the earliest seen in natural pearl cores, related to the expected, suggestively modified cells? There is no reason to expect such observable luck… In fact, just about anyone expects that much will have happened before any pearl gets made—and such events (cell specialization or displacement) are difficult enough to work out in common, convenient, disposable samples. For natural pearls, mounting the logistics for field collection of these rarities is quite something. Sum total: I would be delighted to have put out there a reminder—spelled out in modern terms, of this old question of the natural origin of pearls—and, no more. Vita brevis.
The collection of samples remaining in the kind custody of the Instituto Andaluz de Ciencias de la Tierra—IACT—in Granada (Armilla), can always produce references for natural pearl structure and cores, suitable to inform on what events might be expected at the origin of pearls...
In a sense, the extraordinary detail accessible by exposing pearl cores, as I have, will always be that much more useful than any non-destructive methods that pearl gemmology [CIBJO 2016] might wish for. However, the two pursuits could not be more different: I could compare what I found in pearl cores against shell samples; gemologists would have benchmark samples of pearls of known origin. I could compare my findings with details from gemmology publications, but not quite—the scale is simply too different. The grays of scans would be intricate and vastly distinct mineral fabrics to me. Should those distinctions matter, then scans might wish to get precise. However, any argument for such precision remains rather academic: I do not expect that the process of natural pearl growth might be charted sufficiently to interpret either type of data recovered from pearls (destructively or non), toward a strong opinion on origin. The ever better characterization of definite pearl types—as done these days—is the more promising way.
Then again, perhaps an academic argument is called for to settle an old matter of trade terms left colourfully hanging:
At the time when the latest hefty news on the origin of pearls was the commercial success of grafting, taken as a spectacular confirmation of the 'sac theory'—proclaiming that the formation of pearl sacs was the one necessary event toward the growth of fine pearls—Henry Lyster Jameson wrote on the emerging nomenclature of 'cultured pearls', not kindly. [2,3] His own idea—that the natural origin of pearl sacs could not be clarified, did not amount to much of an argument for the distinction of pearls. I'd say, unsurprisingly: a decade had passed since he wrote that it would be nice to figure out how pearl sacs came to be; it is not clear how he abandoned the question, much like anyone else had. Today, it is quite obvious that he could not have reached any substantial conclusion, yet the problem was certainly not to be thrown away: results are mainly clumped in the last decade. It is now possible to put the problem precisely: what to look for, and, roughly, how. Vita brevis...
On this note, this blog is now closed. My inbox remains at your disposal.
- On my list, the latest publication mentioning the formation of natural pearl sacs is: Bolman, Jan. The mystery of the pearl. Vol. 39. EJ Brill, 1941. The author contends that no work on natural samples was available then—as now, to the best of my knowledge.
- Jameson, H. Lyster. "The Japanese artificially induced pearl." Nature 107.2691 (1921): 396–398.
- Jameson, H. Lyster. "Japanese Culture Pearls." Nature 108 (1921): 528–529.