I have many natural pearl harvest videos on my channel...these are OLD videos so don't expect 4K!
But you can see many, many shapes of natural pearls as they are extracted.
Natural pearls CAN BE round, but most are not.
Douglas, outstanding! I could go on at length, but I'll save that for a single observation now.
The common features being these are interpallial pearls of periostracial onset.
The exception being Pearl#1. It's intervestibular of myostracial onset.
One is a HUGE difference in every way from the others. Hinge pearls may be either. Adjacent heart involvement is myostracial while at the end of the mantle is pallial. Heart (periocardium) pearls are often granular, while pallial pearls are highly nacreous, thus supporting pallial/periostracial onset. The pearls are somewhat loose in support, easily reflected revealing both aspects of the mantle.
Pallial mantles build shell area and volume. Vestibular mantles are specialized to build the surface for the adductor muscle to attach.
Pearl#1 is tightly set within a sac adjacent to the adductor muscle. These pearls often candle/xray with little or no visible nuclei, mainly from strains but for other factors too. Usually anatomical and physical, not necessarily environmental. Pallial lesions are almost always environmental.
This video also demonstrates the value of perimortem pathology and analysis. Sadly in the real world much of the scientific value of a pearl is lost once a pearl is removed from it's situation.
All of these present as natural, irrefutably. Large sizes, uniform structures and lustrous nacre.
Thank you Douglas.