Final reposting for the photo in Post 9 is done (no punctuation in the name). Let me know…
Only Natural: Appreciate the solidarity.
Kima represents a fresh start for this gem, more consistent with its peers and with its quality. Sometimes the most sensible ideas are also the most obvious!
I would maintain 'Tridacna' for non-gem-quality, such as Pearl of Allah (in large and small versions) or plain-surfaced specimens that require lab analysis to differentiate from carved shell.
Regarding rarity, that goes hand in hand with demand, which at this point is spotty for this species. But the best quality, such as Only Natural's specimen above, has a steady if not ultra-high-profile clientele. Pricing at source is comparable with a wide range of naturals (per carat or per gram), to this point without a lot of differentiation per quality. That represents some opportunities for the savvy buyer.
Hubert Bari in
Pearls and a popular
EBay seller testify to the rarity, but do not manage to show top quality. These would not be an example of
Kima to my thinking, although certainly they are Tridacna. Pricing at the EBay seller is also extremely low, but perhaps appropriate for the quality.
Another aspect of Tridacna is its occasional stand-in status for two of pearldom's most mythical pearls: Coconut and Nautilus. In the former case, pearls of plain white surface such as the one linked in the previous paragraph are proposed as calcified vegetal concretions,
"mustika" objects fetching astronomical prices in the Indo-Pacific area. In the latter case, which we now propose as
Kima with flame and chatoyant halo, 'carefully documented' examples have been traded commercially and/or certified as Nautilus by reputable gem labs—including the 'Nautilus' published in Bari's
Pearls.