This is a short entry but I believe it may be of value to some; this entry originates from an email I recieved just a week ago, but we’ve received this type of e-mails several times before… so I will take this opportunity to forward this information to the widest audience possible. The e-mail I recently received comes from the “old continent” and says:
I’m writing from Spain to ask you:
Some time ago I had lunch at a seafood restaurant and I found a pearl inside a clam. It’s small but roundish and pink colored. Does it have any commercial value?
Thank you and kind regards,
Interesting discovery… but to know for sure if it is of value we must first have the following information:
Was the pearl found in a cooked clam (baked, fried, steamed)? A "cooked pearl” can lose its value because it loses its beauty when damaged by heat.
The species that produced the pearl (its proper or scientific name): Most clams do not produce “true pearls” but instead produce "calcareous concretions" which have no real commercial value.
Size and weight of the “pearl”: pearls have a greater value after attaining a minimum size (5 mm) or weight (0.5 g); if the weight/size is lesser than this size-weight, then the economic value is not very significant, but: You have have found a pearl! You’re lucky: natural pearls are rare.
If the pearl is nice and large enough, you can have a jeweler incorporate it into a ring or pendant, as an "accent" for it.
Greetings from Mexico
Effect of Heat on a Pearl
All pearls have an amount of water content in their chemical composition (usually from 2 to 5%), and this water is important to maintain the integrity of the nacre in the pearl. Pearls are made of concentric layers of this nacre, which in turn is made from flat, hexagonal-shaped crystals of aragonite (a variety of calcium carbonate) which are bound or “glued” toghether by means of a special protein (conchiolin), which keep the layers of aragonite togheter.
If a pearl is overexposed to heat, it will loose some of its moisture and may fracture and may also become dull or opaque… and if any of these things happen, the pearl may lose its value (in whole or in part, depending on the degree of damage).
Most people associate the pearl as a nacreous gem, although with the massive amounts of imitation pearls (faux perles) and processed (bleached) pearls available, many people associate the pearl as a shiny white sphere (with the look of polished marble). But the fact is that pearl oysters and other mollusks with pearly shells produce pearls in the “traditional” sense: nacreous.
But there are those mollusks that do not produce a “pearly shell” and have a shell that looks more like porcelain, and these organisms are said to produce "calcareous concretions" which are basically "non-nacreous pearls". These porcelain-looking “pearls” are made primarily of calcite, another form of calcium carbonate (usually found in marble, limestone, bone, seashells and eggshells).
However, some species of mollusks are capable of producing non-nacreous pearls that have very special features, such as those from the “Lion’s Paw” scallops (Nodipecten subnudosus), various species of snails (including Strombus sp.) or the “Giant Clam” (Tridacna sp)… but these are exceedingly rare.
Thus, it is vital to know the species that produced the "pearl", and you will have an easier way to know if your pearl could have some “real value”… or if will only have a “sentimental value”. In either case you can consider yourself lucky.
Size and Weight of the Pearl
These two indicators are very important to obtain the value of a pearl. Large pearls have always been rare and therefore command a greater value, thus a pearl with size of less than 5 mm in diameter may not have a great price, while one exceeding 8 mm will have a good value. If your pearl is small, it is better to just keep it… but if it exceeds 10 mm (diameter) you may already have something of value (Note: in addition the pearl should be beautiful and not have cracks, size is not everything).
And although a pearl’s weight is related to its size in a very direct way, this is not always true; such is the case of the so called “Gas Giants”. These pearls can reach very interesting sizes (12 mm and up), but they really possess a thin layer of nacre, and inside have a kind of "organic mud", putrid and foul-smelling… not the type of pearl you want to give away or acquire. These pearls usually have a large size and display a low weight.
The Pearl’s Beauty
For us the main attributes to consider in a natural pearl are:
Physical Integrity: the pearl does not have any cracks or fractures, that its nacre is intact (undamaged).
Size and weight: that its size exceeds 6 mm in diameter and its weight corresponds to its size.
Beauty: even if you have the two previous attributes, the pearl must be beautiful. If it is not beautiful it has got to have some exceptional trait that will give it value; such as the gruesome but Huge "Pearl of Allah", or like the pearls of the Nautilus for their unusual spirals and origin.
We have to consider that the person who finds a natural pearl is very fortunate (and by this I refer not to the cultured pearls that are placed inside a farm-raised oyster/mussel, and sold in little cans) and even if their pearl may fail in one or more of these indicators, this does not mean you don’t have something special and unique!
If you’re one of the Lucky few: Enjoy your pearl! And, if you are not one of them: what are you waiting?!?! Go to your favorite seafood place and gulp down a dozen raw clams!!!