How rare is translucency in pearls

[Lagoon Island Pearls]

I find your answer utterly fascinating; I love it when we can begin using hard numbers to evaluate as so much about the pearl industry is in constant flux. How do you measure the percentage of calcite in a pearl to come to these numbers?

Thank you, and I agree that by applying math and science we can arrive at useful ways of interpreting data.

If I may bore you with some historical details first, you may better understand how this process is evolving and very much a work in progress.

I have the great fortune to live and work in a pristine ecology, where my target species abound. As we all know, having exclusive access to a resource does not always mean we'll act in the best interest of sustainability. Over the centuries, the derby style of profiteering from natural pearling was the priority with little or no regard to impact, recruitment or data.

Up until now, for all intents and purposes, natural pearling is not sustainable. This is why, to succeed it's been incumbent upon me to find new ways to minimize the sacrifice by putting the welfare of the resource before profit. In most of my field tracts, I have isolated blocks for research only. I'll examine, enumerate, tag and record data based upon examination of live animals by being opportunistic. Catching them while opened, palpating the known growth points, marking them, then allowing them to carry on as they were. My data consists of size, age, gender, s e x u a l (bad word filter.. lol) activity and tissue quality. When a natural pearl is found in a mussel, the animal is assessed for sacrifice or not. Mussels with tiny pearls are tagged with a separate number that I may return later to find the pearl has grown or changed in another way. This is done by numbered ribbons or a binary encoded stainless steel tag tied to the byssal strands, that I may find it later with a metal detector. For bigger pearls, sacrifice is imminent, but the total harvest always remains within legal allowable harvest of recreation harvest limits. I am able to repeat this openly, because the general public is not permitted to harass or molest shellfish, nor may any part of any legal harvest be bought, sold or bartered. If a person wishes to find their own pearl they can, but a limit of 25 mussels per day is imposed. The chances of finding anything worthwhile is near zero. Storms might be the bane of any farmer or fishermen, but they provide an opportunity for me. I have a special rider applied to my permits, where I may harvest pearls from otherwise dead or dying shellfish cast upon the beaches. I sacrifice only on three conditions. Either the pearl is big or the tissues are candidate for tissue graft experimentation. I will admit to some small tracts for sacrifice only, but these tracts are carefully monitored for recruitment and important data is gleaned with regard to incidence of natural pearls, sex, size and overall health. Pearls is not all I do with mussels. Public health and safety (red tide monitoring), biomedical research and ocean acidification effects are experiments that can only be conducted by sacrifice.

In return for this privilege, I provide important data and samples to the powers that be for other purposes. While some of my data and methodology is proprietary, the overall body of my work is open source and intended to be used as examples for sustainable development and education. This why I'm not hung up on secrecy or ethereal concepts and make no bones about speaking openly about pearls and how they come to be.

I've been hoarding my inventory for this very reason, but sooner or later I'm going to need to unload much of it to pay for this operation, which needless to say is quite financially burdensome. I do not feel the need to wholesale my lot, because the concept of buy low and sell high does not appeal to me where nature is concerned. The value added benefits ought to be enjoyed closer to home, rather than further enrich those who are solely driven by profit. To the average farmer, this isn't doable, because too much time is invested in creating a raw product, but pearling is different. I am only able to harvest in limited windows of time, leaving me with other opportunities to examine what I have.

Now, all that said, it would be a crying shame to have this inventory without gleaning some valuable data. To get back to the importance of your question and to add to Mr. Wise's inquiry, I will now touch upon the translucency of natural pearls and how I arrive at evaluating their quality.

As you may already know, I have posted some other topics. Two important ones being Candled Natural Pearls and Fun with Color Pallets!

Each thread was intended to be a guide for education to identify natural pearls, their origins and how they compare with other pearls from around the world. Once one has thousands of pearls in a jar and reams of pictures in a folder, upon examination... patterns emerge. This type of analysis is largely subjective, but I realized with a little scientific support I could create exemplars for comparison. Measuring the passage of light in gems is nothing new and many of the same principles apply, especially when compared to known studies.

I've been gradually gaining traction over the years with some pre-eminent scientists and reputable labs, especially those with electron microscopy and stratigraphic capability. I'd be remiss to not mention Ana Vasiliu, who has been instrumental for her collaborative work at the paleontology lab at the U. of Granada in Spain and the discussions surrounding this research. My brother sells, installs and calibrates analytical instruments (for a Swiss company) for industry and provides access for polarography (chemical content) and water quality. Openly revealing these findings does not dispel the mystery of pearls, but in fact creates an exponentially large volume of new questions posed for study. There is simply not enough time in the day or availability of the equipment to get around them all.

Now, let us take all these points and put them together in a meaningful way.

From my work, I've established known exemplars. These are largely mathematical based on transects of imagery (ie) area volume of ordered crystals v random structure analysis. In pearls of identical size shape and color, I seek high and low thresholds. Lux can be measured with calibrated light, instruments or digital imagery using Photoshop. Once upper and lower limits are established, new samples can be brought in for comparison and the differences can be determined using simple algebra. Is it wholly accurate and fool proof? Absolutely not, but at the very least it replaces much of the subjectivity with objectivity.

Beauty will always be in the eye of the beholder, but to me even the ugliest of pearls have a special beauty in how they came to be and how they measure up with other pearls.

 

[MSC]

Always an interesting read from you, Dave. Here's a question: could you look at the crystal structure of a prepared pearl specimen (a bisection or similar) with use of an scanning electron microscope? Many universities have them. Sounds like the polarography is different but similar to stable isotope analysis with mass spec. I had never heard of polarography before today.

 

[Lagoon Island Pearls]

Here's a question: could you look at the crystal structure of a prepared pearl specimen (a bisection or similar) with use of an scanning electron microscope? Many universities have them.

Indeed they do, but there are costs, require an operator and program within the curriculum. Rather than go on a long winded explanation, here's a link to the latest report from the lab. Lab Report 2014-09-20. It has some bearing on this discussion, but also upon many other discussions and focused on the rare relationship where aragonite and foliated calcite are present in the same structures and the expression of colors. Without straying too far from the topic at hand, it was first thought the green color in Pododesmus macrochisma pearls was secondary to translucent growth first, but the SEM views clearly show the color comes first, then the clear layers follow. New growth is protein rich and obviously pigments are introduced into the matrix. Aragonite or calcite crystals are virtually colorless, but do pass light in ordered frequencies... hence what we know in the pearl world as "orient".

There are other images in the report that clearly show the absence of nuclei in myostracial pearls. FYI, most nucleated pearls are periostracial in origin. Myostracial pearls are almost always more translucent than the latter.

Sounds like the polarography is different but similar to stable isotope analysis with mass spec. I had never heard of polarography before today.

Polarography aka voltammetry is used mainly for trace analysis with greater accuracy. Infinitely more accurate than mass spectrometry or gas chromatography. It's not so much the pearl itself that's targeted, but the pallial fluid surrounding it and then compared later for ongoing changes or as mentioned earlier... water quality.

Here is the manufacturer's description. Trace analysis and metal speciation with voltammetry

 

[Richard W. Wise]

Dave,

Have been remiss in not visiting the forum. Dave, your percentages are very interesting. I take it this is something you have developed and is not based on any other texts? I am thinking, given the exotic nature of your species, that this list cannot be applied across the board.

Your information about the percentages of calcite and degree of transparency is most enlightening

Yes Caitlin I am researching Secrets II which will have a chapter on natural pearls along with jade and a few other gems not covered in the 1st edition. The 1st edition, 2nd paperback printing sold out about a month ago. The book had a 13 year run for which I am most grateful.

 

[Lagoon Island Pearls]

I take it this is something you have developed and is not based on any other texts? I am thinking, given the exotic nature of your species, that this list cannot be applied across the board.

Your information about the percentages of calcite and degree of transparency is most enlightening.

Natural pearls considered for market ought to follow a scheme that provides tangible evidence as to why they are priced accordingly.

Geometry for example, is applied to pearls. Closer to perfect roundness increases value. Measureable refractive indexes imply value to other gems based upon the frequencies and levels of passed light. Statistical mathematics are used to imply rarity of occurrence, even in the absence of grade. Subjectively, a single calcareous pearl from a cephalopod is infinitely more valuable than a near perfect pearl from a quahog (for example) of equal size and shape.

A clam is a clam is a clam. For reasons of value, I would like to believe my pearls are something unique, but they are not. Epithelial behavior is what it is across the board. Pearls form for the same reasons in Antarctica as they do in the Australia as they do in Alaska. There is no evidence to support that the structure of a pearl is in any way proportional to the latitude of it's origin.

Most of us only see the graded ends of any harvest. It's incomplete data and cannot accurately reflect the occurrence of all pearls. Over the years, my discussions with natural pearl harvesters have brought me to the conclusion that their descriptions of bulk lots at the time of harvest are virtually identical to mine, even though the species and colors are different. The greatest percentage are "seed" pearls. Tiny pearls from 1-3mm in all shapes, sizes and colors. A few percent of each harvest are larger, higher quality gems.

There is an indeterminable number of events in any combination that give rise to pearls. A single species can produce pearls of any size and any color, although it's fair to say certain colors and shapes predominate. I have found dark peacock hues which rival Tahitian pearls along side of highly translucent whites within millimeters in the same animal.

You've posed a challenge as to why translucency occurs in some pearls and how value can be applied. I attached a link to a recent lab report (although monetary value is not in the discussion). The pearls in that report were examined using SSEM by colleagues at the paleontology lab of the University of Granada in Spain. Like yourself, they often pose similar challenges and receive samples from my field work. Very often parallels are drawn to other known species and in almost every instance are considered analogs, not anomalies.

My reasoning for presenting this report is to demonstrate a known difference in cause among the same species. That being myostracial and periostracial origin. Myostracial pearls are almost entirely internal. They form deep within the tissues, in nearly complete absence of visible nuclei or physical factors like foreign bodies such as large parasites, broken shells etc. Mysostracial pearls are almost always auto-immune in origin and the need for the production of a water-tight barrier or soft tissue cushioning is non-existent. These onset of these pearls commence with the bare minimum of behavior at a periostracial level, instead almost immediately at a prismatic level, then morph into nacreous structures.

Periostracial pearls occur when external factor(s) are present, where there is a necessity for isolation from water, or other pathogens and/or parasites. As such, the periostracum forms in a highly proteinaceous manner. Once those barriers are established, epithelial behavior may morph into prismatic and nacreous structures.

Pigmentation occurs in protein which are periostracial and interlamellar factors. Aragonite may have slight coloration, but for purposes of this discussion it's quite clear. At the opposite end of the growth scale, pearls greater than three or four years in growth are very often occluded in calcite, as programmed cell behavior present with apoptotic or senescent characteristics.

I'm not sure "other texts" exist. If they do, they've been suppressed, but that would make no sense because they'd be supposed to adequately represent the real value of a pearl to a lay person who is purchasing pearls. Like archaeology, the greater part of scientific value is lost when the object is no longer in situ. Traditionally, natural pearls go from shell to market with little or no consideration of anything other than short term economics. To me, that is tantamount to reckless abandon and it's no surprise world wide stocks are greatly endangered. I could never operate under those circumstances, legally, morally or ethically. To me, pearls are not just baubles for luxury and vanity. They are affirmative indicators of changes in our environment, examples of building blocks for creation and evolution and keys to higher learning for biomedical research and longevity.

 

[whicker]

Terrific report and description of your work!

 

[Richard W. Wise]

Dave,

Aside from their value in research, pearls are also objects of great beauty, but of limited utility. No one needs a pearl. They have no nutritional value, won't keep off the rain or keep you warm in winter. Market considerations include aesthetics and remember, utility is not, thank the gods, the only sort of value.

I enjoyed your discourse.

Richard