Is the Pearl I found in my Clam/Oyster/Mussel Valuable?

This is a Special Educational entry, but I believe it may be of value to some of our new visitors; it originates from an email I received just a week ago, but I have received this type of e-mails many, many times before... so, I will take this opportunity to have this information to the widest audience possible. The e-mail would say something like this:

I'm writing from X country to ask you:
Some time ago I had lunch at a seafood restaurant, and I found a pearl inside a clam/mussel/oyster.
It's small but roundish and X colored.
Does it have any commercial value?
Thank you!​

And this is a remarkably interesting thing to find out, and each pearl would be a unique case, a unique study in itself. Let us start by analyzing some of the things that we could consider in order to know the value of this "seafood treasure".

Effect of Heat on a Pearl
Was the Pearl found in a cooked animal?
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” together by means of a special protein (conchiolin), which keep the layers of aragonite together.
Dyed FWP damaged by fire (1).jpg - Pearl Damaged by Heat

If a pearl is exposed to heat, it may lose some of its moisture and may fracture and may also become dull or opaque... and if any of these things happen, the pearl will lose its value (in whole or in part, depending on the degree of damage).

Did you Bite on the Pearl?
Ouch! Even if it felt hard on your teeth, pearls are considered "soft" gemstones. On the Moh's Scale pearls are usually said to have a hardness of 3 Mohs (just like Calcite)...and on the top scale we have diamonds (10). By biting on the pearl, you could have cracked it (and hopefully not the pearl AND your molar!) and this could have damaged the pearl, either partially (small fissure, scratch) or completely (major crack, pearl is split!).
Japanese Mabe with cracks (5).jpg - Cracks on the dome of a Mabe pearl

Pearl-producing species
Most people associate the pearl as a nacreous gem, but there are mollusks that do not produce a “pearly shell” and their shells look more like porcelain, and these organisms produce "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). Many people find these pearls inside edible oysters or clams, which are the least desirable pearls due to their very average looks (white/cream colored, dullish). Sometimes they are very pleasant, like the one found by my friend @BajaPearlHunter
Perla de Chocolata (2).jpg - Natural Pearl found in a "Chocolate Clam"

However, some species of mollusks can produce non-nacreous pearls that display distinctive features, such as those from the “Lion’s Paw” scallops (Nodipecten subnudosus), various species of conchs (including the "Queen Conch" Lobatus=Strombus sp.) or the “Giant Clam” (Tridacna sp)... but these are exceedingly rare. The photo shows you what we know as a "Flame Pattern" on a "Conch Pearl"...this is a unique trait, and quite beautiful!
Perla de Chocolata (2).jpg - Natural Pearl found in a "Chocolate Clam"

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 particularly 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 fair 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 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 generous size and display a low weight.
Perla de Chocolata (2).jpg - Natural Pearl found in a "Chocolate Clam"

The Pearl’s Value
The main attributes to consider -under this particular case- in a natural pearl are:
  1. Physical Integrity: the pearl does not have any cracks or fractures, that its nacre is intact (undamaged).
  2. Size and weight: that its size exceeds 6 mm in diameter and its weight corresponds to its size.
  3. Beauty: even if you have the two previous attributes, the pearl must be beautiful.
  4. Special Trait: If it is not beautiful, it should have an exceptional trait that will give it value...a unique shape, color, size, species, place.
We must consider that the person who finds a natural pearl is extremely 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 or at "Pearl Parties") 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 unique pearl!