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Crossed-lamellar is an elegant termination of aragonite between the Myo/periostracial and quiescent phases, thus interfacing the prismatic and nacreous phases to a great degree. The movement between these phases are gradual, not abrupt. In fact, this interlocking is the basis for exceptional...

A very important point. Nacreous is a growth phase. It occurs between the prismatic and quiescent phases nine to eleven times a year according to lunar periods, hence layered. This phase involves elegant termination of calcium carbonate, whatever that may be. Although one could, there is no...

Moderately or lowly/slightly are definitely acceptable. My usage of highly was for example, not exclusivity. Quahog (Mercenaria mercenaria) are moderately nacreous. Geoduck (Panope generosa) are slightly nacreous. Indeed, scallops are a better example of foliated calcite structures. I stand...

Calcareous would be true in both scientific and lay terms, but then again to what degree? This is why I'd suggest "highly nacreous" for bright iridescence and orient of pearl oysters, abalone etc. In gemology, calcite is good and bad depending on it's properties, so it needs prefixes to avoid...

For clarity, gastropods and pectinidae (scallops) have some locomotion, even cockles and clams have feet which allow themselves to relocate or reorient, thus irritation can be a factor but there remains the issue of irritation v perforation all the same. A clam kicking it's way around does not...

Yes. Terms like porcelaineous describe appearance of pearls without implying structure. It's common knowledge that ceramics are created in a kiln at a high temperature. Prefixing "non" to a word should only be used in the context of it's opposite. Even in a lay context, it's redundant to suggest...

The tenets of science provide there is no burden to refute something which does not exist. However in this case, the burden is already laid out. There is no need to initiate a methodology, field study, peer review or publication. Let's start here. Although not cited directly in these papers...

Yes albeit not highly (at least on the surface). In every collection, I'll observe one or two percent as highly calcareous. All pearl sacs depend upon a multitude of e-cell types being present. This often varies between pearls, even in the same creature. Most can be picture perfect but others...

I should also add to this. It's actually four stages. Perio/myostracial --> Prismatic --> Nacreous --> Quiescence. In lay terms. Create a water tight barrier --> Build a structure --> Get comfortable --> Rest. Laying up nacre is a phase which is common to most molluscs. The only exceptions...

Me too, while they are country mile from gem quality, they are chocked full of science and wonder. Tiny pearls reveal big secrets!

Shell beads from FW mussels are indeed nacreous. Your point on the difference in aragonitic v nacreous stands to reason. Highly aragonitic ought to be used in a scientific context because it does not default to one aspect (iridescence and orient) while overlooking the other. Highly nacreous in...

I should add that aragonite, especially in winter months or among other species (ie) melo melo, conch etc. can appear perfectly clear. It does not always present with irridescence and orient. Those and colour are factors of interspersed proteins, namely conchiolin.

Highly aragonitic is correct in terms of shell structure where foliated calcite is not present. Perisotracial (conchiolin) --> Prismatic calcite --> Nacreous. These being the three stages of a growth period. While calcite is present in the prismatic phase of most molluscs (and pearls), it's more...

For several years, I've been vociferous to the extent a commonly used term "non-nacreous" is misleading if not erroneous. Between 2011 and 2015, I worked with Ana Vasiliu in the microscopy lab at the University of Paleontology and Stratigraphy in Granada, Spain. Initially our work was to use an...

Outstanding Steve! For a modern assembly, it's scarcely more exceptional than this. Well done, sir!

Thank you for the updated imagery. It's as I suggested. The pearl formed in the viscera then once excessive in size, burst from the sac then became fused to the shell. The margin between the shell and the pearl is narrow, thus it's only been affixed for the latter part of it's life. I'm...

Yeah I've never seen such a large intrusion v available space, especially in the visceral cavity. It's remarkable how the creature pretty much went full term life expectancy, so it was otherwise healthy. Edible oysters in northern latitudes grow quickly and don't live as long as other molluscs...

It's definitely an interesting specimen. The stippled surface is certainly unique having radiating columnar growth fronts. However, I would challenge the "blister" classification. From the limited aspects viewed in the images, it appears to be an attached pearl with a visible surface area...

Having not examined it personally, I'm not certain, but it's most likely tissue cultured. At first they would have had individual sacs. As they grew outward, they competed for the adjacent space. Once the spaces were reduced to a minimum, that part of the sac lost it's vascular viability, hence...

It's not caulking. It's bridging, which is modified epithelial behaviour when voided by spaces having acute angles. When mantles (and pearl sacs) become spaced from the shell (or pearl), they reshape themselves to eliminate any distance between. Mantles and shells must be in direct contact with...