Permit me a little sidetracking (or even better, backtracking) here while awaiting the definitive photos.
Orient?water?etc
I dug into my memory?and the threads?for short-term member Virginia Hatfield's beautiful abalone pearl from last May, juxtaposed below with the pearl in question from Dr. Tom Stern. At the time, I used the term 'water' to describe the seemingly translucent edges of the ab (no doubt aided by the shape of the pearl), giving the impression of a pearl within a pearl.
As it happens, such a 'halo' quality recalls the description of 'orient' by natural pearl traders from whom I have been fortunate enough to receive mentoring?orient viewed as an exceedingly rare phenomenon distinct to the more ubiquitous quality of iridescence/peacock. As each of these characteristics is found in rare and noble pearls, a conceptual association/confusion would logically result.
The concept of water seems clear, while also a bit tied up with 'orient' and 'iridescence.' But to me, this photo of Dr. Stern's pearl simply appears to indicate a faulty and inconsistent outer nacre layer, either from peeling or ill formation. Caitlin, your obvious enthusiasm and experience must earn my benefit of the doubt!