Can Someone Identify...

[painshill]

Most of the pertinent information from Hainschwang (and the malacologist he consulted) is in the thread on the Pearl-Guide forum. For the samples examined:

The composition was aragonite and was non-nacreous.

The aragonite had not altered to calcite, as would be usual in fossils.

It exhibits a cross-lamellar “flame” structure with some concentric layers.

There was no significant core or nucleus.

This gastropod Magilus antiquus is known to produce these kinds of masses by infilling the abandoned spiral portion of its shell.

Magilus antiquus has a wide distribution from India through to the Great Barrier Reef.

The structure is produced by the living mollusc, not by subsequent replacement.

The correct term is probably “calcareous concretion”.

The age from carbon dating was less than 500 years.

Specimens from fossil-aged deposits are known but may be unaltered and not fossils as such.

The world Jewellery Foundation (CIBJO) has ruled that the term “pearl” can in some circumstances be applied to non-nacreous forms (but these particular objects are not formed in a pearl-sac).

This from Wiki:

Biologically speaking, under the right set of circumstances, almost any shelled mollusk can produce some kind of pearl, however, most of these molluscan pearls have no luster or iridescence. The great majority of mollusk species produce pearls which are not attractive, and are sometimes not even very durable, such that they usually have no value at all, except perhaps to a scientist, a collector, or as a curiosity. These objects used to be referred to as "calcareous concretions" by some gemologists, even though a malacologist would still consider them to be pearls. Valueless pearls of this type are sometimes found in edible mussels, edible oysters, escargot snails, and so on. The GIA and CIBJO now simply use the term 'pearl' (or, where appropriate, the more descriptive term 'non-nacreous pearl') when referring to such items and, under Federal Trade Commission rules, various mollusc pearls may be referred to as 'pearls', without qualification.

A few species produce pearls that can be of interest as gemstones. These species include the bailer shell Melo, the giant clam Tridacna, various scallop species, Pen shells Pinna, and the Haliotis iris species of abalone. Abalone, or Pāua are Mabe pearls unique to New Zealand waters and are commonly referred to as 'Blue Pearls'. They are admired for their incredible luster and naturally bright vibrant colors that are often compared to Opal. Another example is the conch pearl (sometimes referred to simply as the 'pink pearl'), which is found very rarely growing between the mantle and the shell of the queen conch or pink conch, Strombus gigas, a large sea snail or marine gastropod from the Caribbean Sea. These pearls, which are often pink in color, are a by-product of the conch fishing industry, and the best of them display a shimmering optical effect related to chatoyance known as 'flame structure'.

Somewhat similar gastropod pearls, this time more orange in hue, are (again very rarely) found in the horse conch Pleuroploca gigantea.

The largest pearl known was found in the Philippines in 1934 and is known as the Pearl of Lao Tzu. It is a naturally-occurring, non-nacreous, calcareous concretion (pearl) from a giant clam. Because it did not grow in a pearl oyster it is not pearly; instead the surface is glossy like porcelain. Other pearls from giant clams are known to exist, but this is a particularly large one, weighing 14 lb (6.4 kg).

Thank you all! Yes mystery solved. I'm not a member but was there anything else said in the article... I'm very curious

Edited September 17, 2013 by painshill

[elcoincoin]

Painshill is deifinitly the man when its about resolving nature enigmas !

Reminds me the thread bout that lookalike stone shroom from australia!

Hats off !