Could this be a Tridacna Gigas Pearl?

by Dermot

Large Object Found in Clam

Large Object Found in Clam

This object was found in a giant clam shell in the Philippines. What is it? Could it be a pearl? It obviously doesn't look like a pearl, but could it be one?

The piece is most interesting with the shape of the inside of a tridacna gigas shell, but I just don't see how it could grow that way without being totally attached to the shell.

Tridacna Gigas Object
Tridacna Gigas Object

We spent the day running around speaking to any geologist and malacologist who would see us. They were all impressed by the specimen, some calling it beautiful, but none had a definitive opinion as to what it was exactly.

Some of the opinions we got were: a deformation of the tridacna gigas shell itself; a calcium deposit of some sort; a bone formation (?)...well, that's about it actually.

Tridacna Gigas Object
Tridacna Gigas Object

The consensus was that it isn't a pearl, however. They were all anxious to send us somewhere else, of course, including the international conchology conference coming to Paris on March 7-8. I think we will see what we can find out there.

Tridacna Gigas Object
Tridacna Gigas Object

In the meantime, one of the geologists we saw was kind enough to take a few pictures of the object that I have attached to this email in the hopes that you would consider posting them on your site so that some of your learned visitors may share their opinions as to what this striated, very dense formation could be...? What do you think?

Tridacna Gigas Object
Tridacna Gigas Object

Alternatively, or in addition, if you have any contacts who specialize in strange formations that may occur in mollusks I invite you to share these pictures with them as well (btw- the coin that is in the photo is a 2 Euro piece which is almost exactly 1 inch in diameter).

Comments for Could this be a Tridacna Gigas Pearl?

Average Rating starstarstarstar

Click here to add your own comments

Sep 15, 2014
giant gigas tridacna
by: Anonymous

good day, I wish to sell my giant Tridacna pearl weighing 5.25 kgs, 43 inches in diameter, 8.5 in length.

Aug 19, 2013
Thank you for you comments
by: Kari

Hello Hadjzad Biteng,

Thank you for your comments. They are much appreciated and respected.

Jun 12, 2013
The object is a Tridacna Gigas Shell
by: Hadjzad Biteng

Highly respected friend,

From reliable sources, the said Tridacna Gigas Pearl, as shown in the pictures is NOT A PEARL, it is a clam shell. They found the Tridacna Gigas shell while digging a deep well and making it look like pearl by polishing the shell smoothly. Stories spread all over the place that they found a big pearl in the forest.
Actually the place where they found the Tridacna gigas shell is noted for Tridacna Gigas fossils.

Thanks, God bless.


Jan 23, 2012
by: Mr. Biteng

Hello Kari,

Good morning and have a nice day!
The Tridacna Gigas Pearl look like a clam shell. Yes it is not a PEARL. They fake and manufacture this pearl from the Original Tridacna Gigas (Giant Clam)Shell. The clam was found in one of the farm while digging deep well in Ungsus Matata, Tandubas, Tawi Tawi, Philippines. And They polished with sand paper and started making this look like PEARL. They brought to Bangao Tawi-Tawi and to Zamboanga City, and it spread like fire.


Apr 14, 2010
Expert opinions
by: Dermot

Hi Kari,

We brought the object to the international conchology conference here in Paris last month and had the opportunity to show and discuss it with some very knowledgeable people.

Though the consensus was that it is a very interesting and beautiful object, it is most certainly not a pearl.

What it is, apparently, is a very old, petrified piece of a Tridacna Gigas shell that has been worn and smoothed by centuries of sea-bed currents.

We would be open to the idea of selling the object to a knowledgeable collector who could appreciate its natural beauty and paleontological particularity.:)

Feb 26, 2010
Horizontal growth rings
by: Dermot

Thanks again for your help and advice.

The shell, apparently, was left at the bottom of the sea (it is very large..about a meter in diameter) and, though it could be brought up,

The fact that there are no signs that it was cut out of the shell has always baffled me as well. How could something like this form to the shell without attaching itself and requiring it to be cut out..? Strange.

The piece is about 31 cms long (a little over 12 inches) and 5-6 inches wide.

It weighs about 10lbs. It is quite marble. It's surface is somewhat gritty but smooth to the touch .. like a polished stone. It's color is off-white, like a very old marble statue or bone, for example.

Another odd thing about it can be seen in the picture with the left corner, it has been damaged and appears as though a piece was chipped off. The smoothness of the surface is gone revealing a rough, porous, stone-like interior. Seems to suggest that the smooth surface is the result of long-term erosion.

The growth rings or striations are quite interesting indeed, otherwise I would just guess it was a piece of eroded stone or marble of some kind. I know exactly what you mean about the concentric formation of pearls...this appears to have formed in consecutive, horizontal layers, presumably over an extremely long period of time. I suppose it still could be some kind of sedimentary rock formation but how long would that take?? and how/why would it form inside a shell? Very odd.

Thank you for the information regarding the jewelery conference in Switzerland. It may be worth a visit...maybe I'll see you there :)

Thank you again Kari. I will keep you posted as we learn.

Feb 26, 2010
Interesting specimen
by: Kari

I'm glad you were able to get some feedback on your specimen.

Although it does not "look" like a pearl, if it in fact grew inside of a tridacna gigas (giant clam) shell, then, in fact, it may be a pearl, although the shape is very unusual with how it matches the inside of the shell. I don't suppose there is any chance that the shell has been saved?

It does not appear to have been cut off, does it? I don't see any cut marks from the photos. Do you see any on it?

How much does it weigh?
What are the dimensions?

It helps to have the 1" Euro coin and the photos of it being held to show the size, but it would also be nice to have the measurements.

If you can get to the conference in Paris, that would be your best bet at getting it identified.

March 18-25 there is Basel World in Switzerland which is a large jewelry show. Many pearl experts go to this show and if you can get there, you might also be able to learn from any pearl experts you could meet there.

I was looking more closely at the photos and the growth rings. Pearls have growth rings starting in the center and spreading out in concentric circles to the edges. On the photo, the growth rings look straight along the edge which is indication of shell growth.

At any rate, it is a rare and unusual piece and I would think it would be of interest to collectors.

Feb 26, 2010
Thanks for advice
by: Dermot

Hello Kari and thank you for your advice.

I will do as you suggest and try to find a local opinion...though, in my experience, it is next to impossible to find a reliable opinion of anything here in Paris.

I will let you know if/when I am able to find some answers.

Feb 26, 2010
You are right, it doesn't look like a pearl.
by: Kari

It's a very interesting object, but I agree with you, it doesn't look like a pearl. I suggest you show it in person to someone local and get some more opinions.

Click here to add your own comments

Join in and write your own page! It's easy to do. How? Simply click here to return to Giant Clam Pearls.