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If there is anything in the scientific literature that concisely and transparently defines nacre in such a manner I would want to be the first to see it.

At this point we must agree to disagree. I will be sticking with the terraced/columnar organic secretion models that result in iridescent phenomenon. But will happily campaign for the true-pearl status of 'porcelanous/porcellanous/porcelainous' specimens.

OK so per Douglas' suggestion above, what would be the percentage? The aragonite platelet model of nacre would be differentiated by its organic component. If only our unidentified porcelainous pearls had such a layer!

Yes the low organic component of crossed-lamellar shell material has frustrated all our attempts at genetic extraction for pearl species confirmation. But the issue of 'degree of nacreousness' is still eluding us. What percentage should be assigned to crossed-lamellar shell material, assuming...

This is a very helpful observation. It is still not clear how we can speak of percentages or degrees of nacreousnous. Whether expressing as iridescence or not, nacre is nonetheless nacre. "It either is, or isn't, nacre." My conclusion here is that a crossed-lamellar pearl such as Conch that is...

Are these percentages / degrees of nacreousness referring to the distribution of microstructures throughout the different regions and layers of a shell? If not, can we clarify how nacre, crossed lamellar, prismatic, etc can be secreted together as a homogenous amalgam?

Once again we are dealing with ambiguity that defies understanding. Terraced or columnar aragonite platelets, carefully organized and secreted by the mantle, comprise nacre. It either is, or isn't, nacre. Crossed-lamellar is the anti-nacre, perhaps even the prototypical 'porcelainous'...

I am continuing to have difficulty with the ambiguity. "Highly Nacreous" suggests that there are degrees of nacreous expression, such as "Moderately" or (dare I say) "Non." Aragonite tablets/platelets arranged in terraced (Bivalvia, Cephalopoda) and columnar (Gastropoda, Cephalopoda) forms...

Porcelanous/Porcellanous/Porcelaineous. I was going to include the third English spelling option but was afraid of too many slashes! In all due respect, I do not think it is clear to anyone but a biomaterial scientist (and that does not include me!) about the nature of nacre vs. porcelaineous...

The point is that nacreous refers to all mollusk shell construction resulting from an organic process preceding and directing tablet and fibre crystallization? I just looked up etymology for nacre and among its possible origins is the Arabic naqur (hunting horn), the shape of a mollusk shell...

The assertion is effectively and empirically refuted. It seems as though it comes down to who has the burden of proof (as in a court of law), the gemmological sector having reached its conclusions. We need to organize!

Dave, You will be anticipating this post… Below is a report from Nature (10/17/1912) regarding the pearl gifted to T.H. Haynes (pioneering Australian pearler) by the Sultanate of Sulu in 1884. As all such reports over the centuries of pearls from the 'pearly' Nautilus, it was porcelanous and...

Is this the interpretation of FW shell beads from mussel? While colorless and non-iridescent, they are regarded as nacreous and thus compatible as nuclei (although now it seems the range of successful nucleus material is wider than long thought). Is an argument in favor of the existence of...

Fantastic post! On the above statement, where would 'highly aragonitic' fit in? I'm thinking about non-nacreous aragonite/calcite microstructure generally referenced as crossed-lamellar and characteristic of the 'flame' phenomenon. No doubt my thinking could use updating…

A new forum was indeed created: This new forum was launched without fanfare and has yet to be discovered or utilized in any significant way. Scientific and what might be called 'existential' posts naturally occur in the course of a thread. But there are times that a subject may merit a thread...

Dave, thanks for the compliment! As hinted in a prior post the assembly has been successful in large part as an expression of the pearls themselves, versus following some preconceived notion. The execution is masterful, as the settings remain subservient to the pearls. I can't tell you how many...

As for a second opinion, lab certifications are only of value for verification of natural origin, along with informed species conjecture. Neither is applicable in your case. In my view some researcher should be offering you a cost-free avenue for studying the specimen in a non-destructive manner.

Agree, hoping to see an exterior point of entry image. It's easier to imagine an external onset as otherwise you'd think the oyster would have found some way to expel the irritation. Makes me gag looking at it! Very interesting surface, everyone should take a close look. Any speculation on age?

Closure for the Alex Collins Poe Pipi lot project! As a quick reminder, here is an image of the pearl material: 1) 110 carats Poe Pipi collected by Alex Collins in the Tuamotus; and 2) a hank of 3mm Poe Pipi collected years ago for an abandoned project, serendipitously in the hands of our chosen...

Just to answer myself here, measured blister dimensions and cubic density of the shell material would provide the resulting estimate.