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These blisters are formed under the adductor of the left valve. They're not rare, in fact quite common across many molluscan species. They are largely idiopathic (unknown cause) however these present along the medial aspect of the muscle scar as opposed to entirely surrounding it, thus ruling...

Jeremy has included an early natural freshwater strand for comparison, which is clearly that. Graded for size (graduation) first, then luster, color and shape by lessening degrees. Each markedly dissimilar at the nuclei. This is what we'd expect from most natural strands, especially ones created...

Commercial or recreational? Licensed by the state Department of Marine Resources? Recreational harvesting may complicate matters. These are natural quahog pearls, hence the species of origin is not in question. However, some value (albeit scientific) is lost when the pearl is removed. I would...

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This is not a pearl by any description. More likely a slingshot round.

You have done well given your tools. Each of these views reveal subsurface contrasts consistent with bead nucleated pearls. This is otherwise known as periostracial growth. It's the first growth expressed by most molluscs in any shell building process. It's mainly protein which generally...

Though the images are improving, I'm still seeing equal diffusion at the subsurface and complete absence of distinct contrasting at the nucleus. For those reasons, I'll suggest this is a bead nucleated cultured pearl. Nevertheless, it's a large, well formed SS pearl in good condition.

Thank you, Douglas. Are your naturals P.sterna? I'd really like to see an array of views from those and other species. Same for Gulf pearls, if anyone is inclined to that. Surely someone somewhere has a lot suitable for the task. If anything, this technique demonstrates dissimilar contrasts...

And a few others.

Thank you! A few more.

It's a good start. The first image not so much, the second not as bad and the third is somewhat better. First glances of the second and third image shows a patch of conchiolin just below the surface. While I can't see distinct geometry at the edges of the pearl, I'm leaning toward bead...

And a few more

I've updated the OP and here's a few more.

GIA is a good option, as is SSEF. Both use well defined x-ray views to examine an object. In this case, likely different views to determine the presence of a shell bead. In the absence of that, they'd look at the inner volume for the presence of grafted tissue, geometry of growth stages, foreign...

I would normally refer you to this thread, but it seems the images are different from what I've posted. Forum software update bug, perhaps? Candling reveals the nucleus. There are marked differences between natural and cultural formation. Views of bead nucleated pearls typically show juvenile...

Appraisal is subjective and you'd find a wide range of opinions in the absence of true expertise. 11-12mm is quite large for a natural pearl. That's bad and good. Bad being it's likely cultured, good being it will have some value if deemed natural. The provenance of this piece is questionable...

It may or it may not be conclusive as Jeremy mentioned, but it's worth a try to see if there are common or distinct features.

I may have hoped the Smithsonian had a more astute comment. The premise being pearls form around foreign objects in every scenario is largely false. Then again, the displacement and modification of epithelial cells or the autoimmune behavior thereof tends to go over a lot of heads, but one...

Lab certification is generally used to affirm the origin and species of natural pearls. Both are known, hence authentication is not necessary. If anything, may needlessly inflate the base price.

A simple reality. Small pearls rarely become the centre piece, instead very often as accessory stones to other larger stones. Small pearls need a value add or they just don't move. Despite the OP's pearls being reasonably lustrous, nicely shaped and rich blue/purple colors, it would be very...