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:
Good morning:
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,
Marta
My answer:
Hello Marta,
Interesting discovery… but to know for sure if it is of value we must first have the following information:
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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.
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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.
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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.
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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).
Pearl-producing species
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:
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Physical Integrity: the pearl does not have any cracks or fractures, that its nacre is intact (undamaged).
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Size and weight: that its size exceeds 6 mm in diameter and its weight corresponds to its size.
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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!!!
Myth #2: The Aquaculture of Pearls in Spain
It is fascinating to meet with people from all over the world, specially if they are seasoned travelers…they always have interesting stories to share with us and we appreciated their talk and sharing of experiences, specially when they have previously visited other pearl farms in Japan, Tahiti or Australia EXCEPT when someone comes up with their “Mallorca Pearl Farm Visit”. The typical description is that they have seen divers retrieving the always perfectly round pearls that seem to come in only 4 basic colors.
Spain is, indeed, a great aquaculture producer…but its main products revolve around edible shellfish production: scallops, mussels and edible oysters. These species of bivalves are usually produced in the northern part of Spain, on the coastline of Galicia, where they grow three very tasty and valuable species: the Mussel (Mytilus galloprovincialis), the “Vieira” or Queen scallop (Pecten maximus) and the european rock oyster (Ostrea edulis). But none of these species are able of producing nacreous pearls (they would produce “calcium concretions” or “non-nacreous pearls“) so they cannot look like the “Mallorca Pearl”. Let us look into this more closely then…
The so called production of these famous “european pearls” is found in the city of Manacor, Spain, and… where is this place??? It is a beautiful spot in the Mediterranean Sea (see map, courtesy of Google Earth), an area that has not been known or recognized -not today nor in ancient times- as a great pearl producer. Also, take note that Manacor is on an island…but not right next to the sea but some kilometer away from it. This can only mean then that the pearls and their oysters are being grown in special ponds or lakes or maybe even in rivers… but examining the city with Google Maps or any similar program will not reveal any evidence of large lakes/ponds suitable for a grand scale production of pearl oysters nor mussels.
Very well then… they must grow the pearls and their oysters in the ocean and haul them into the city as needed. What variety of pearl oyster could they use to produce their pearls? Let us do a bit of research…hmm, we seem to find very few sources that include information on pearl fisheries -past and present- inside the Mediterranean Sea. Let us use Sohei Shirahi’s excellent book “Pearls & Pearl Oysters of the World” and let us see…weird… no pearl oysters reported in that area of the Mediterranean. The only information we find is that from another great book -actually a “grand classic” on the subject- Kunz and Stevenson’s (1908) “The Book of the Pearl” which cites that a man by the last name of Vassel states that in 1896 , the “Akoya Pearl Oyster” (Pinctada imbricata) made its way into the Mediterranean by way of the Suez Canal and can now be found in limited areas of Tunisia, North Africa. Yet, there is another pearl oyster in the region: the “Mediterranean Winged Oyster” (Pteria hirundo) which can be found in Turkey and Italy. There is not a single report of these species for the Spanish island of Mallorca. The following map can give us a clearer idea of the worldwide distribution of pearl oysters (based on Shirai, 1994).
Well then, if there are NO pearl oysters nor pearly mussels in Spain nor in its island of Majorca… what gave rise to this myth? It is hard to know, but we all know how half-truths have an easy way of propagating… like summer grass on fire. It is a fact that the Spaniards have always stated that their so-called “pearls” are just as beautiful -or better- than their cultured pearl counterparts, or even state that their product is manufactured using “marine materials” but I have never seen an advertisement or article that states that they “grow” their pearls inside living oysters. But some people are…that is for sure. For what reason or to what ends? You can be the judge. So, let us go to an “official” “Majorca Pearls” website, from where I extracted the following text:
“Majorca pearls are imitation pearls manufactured on the Spanish island of Majorca in the Mediterranean. Local women there have specialized in the artistic fabrication of faux pearls since the 19th Century. These pearls have such a resemblance to the natural cultivated pearls that only experts can tell them apart.”
That last part about only experts being able to tell them apart is a hoax (in future posts we will try to help you identify all sorts of pearls, including fakes…which are very easy).
But for now I believe that it is quite clear that these imitations or “faux perles” are not grown from live organisms, but a product of Human manufacture. But, for those that will still believe otherwise… I have -for the first time on the Internet- a perfectly preserved specimen of the very elusive “Majorcan Pearl Oyster” (scientifically named: Plasticus artifactus). The specimen can be admired at our Museum-like display at the Pearl-Shop in Guaymas, Sonora, Mexico… so stop for a visit, don’t miss on this unique opportunity!
If you have questions or an interesting subject to suggest, please feel free to make your comments known on this Blog…see you in a couple of weeks!