Extraordinarily large non-nacreous pearl weighing 25kg from the giant clam Tridacna gigas discovered in the Philippines

Compared to the weight of Pearl of Allah/Pearl of Lao Tzu (6.1 kg), even if we deduct 5 kg for the weight of the shell/valve, a weight of 20 kg for this Tridacna gigas blister pearl is indeed enormous, and perhaps qualify the pearl to become the largest non-nacreous blister pearl/calcareous concretion in the world. I do not have statistics of other larger blister pearls discovered from the giant clam Tridacna gigas and shall be grateful if any other member/contributor would provide us with these details in this forum.

Another famous blister pearl discovered from the giant clam Tridacna gigas, also from the coral reefs off the coast of the Island of Palawan in the Philippines, the same region where the "Pearl of Allah" was discovered, is the 2.27 kg (5 pounds) Palawan Princess, believed to be the second largest non-nacreous baroque blister pearl discovered from the giant clam Tridacna gigas. The "Palawan Princess" which has an uncanny resemblance to the human brain, is a non-nacreous blister pearl having an approximate diameter of 6 inches (15.2 cm). In comparison the "Pearl of Allah" has a length of 9.5 inches (24 cm). The Palawan Princess was put up for sale by international auctioneers Bonhams & Butterfields at their Natural History Auction, on Sunday, December 6, 2009, under Lot No. :- 2377, and was accompanied by the lower valve of the original giant clam shell in which the pearl was discovered, showing the point-of-attachment where this blister pearl developed. This valve measures 19 by 13 by 6.5 inches (48 cm by 33 cm by 16.5 cm). A pre-sale estimate of USD 300,000 - USD 400,000 was placed on the blister pearl by the auction house.
The images given below are :-
1) Image of the Palawan Princess resembling the human brain.
2) Image of Palawan Princess within its original shell.

The website of Kari Pearls - http://www.karipearls.com - reports of another large blister pearl, still attached to one of the valves of the giant clam Tridacna gigas. The pearl named after its owner "Elias" is known as the "Pearl of Elias." The pearl is believed to have been discovered around 1977, and since then had been in the private collection of the owner. The giant valve (one half of the shell) together with the pearl weighs 87 kilos. However, the exact weight of the pearl alone is not known as it is still attached to the valve, and cannot be weighed alone. Experts have estimated the weight of the pearl to be around 9 kilos using its dimensions - the top surface measures 9 inches (22.9 cm), the height is 7 inches (17.8 cm) and the exposed circumference 23 inches (58.4 cm). In comparison the "Pearl of Allah" weighs 6.1 kilos. Hence, the "Pearl of Elias" appears to be larger than the "Pearl of Allah."
The following images of the pearl are attached :-
1) Pearl of Elias attached to its shell and a replica of Pearl of Allah placed by its side for comparison.
2) Exposed part of Pearl of Elias surrounded by the human hands giving an idea of its enormous size.

Thanks Maryjewel for your update. Comparing the photographs of the "Pearl of Elias" you have uploaded with those of the "Don Gonzales Pearl" leads to the following interesting observations :-
1) While the "Pearl of Elias" blister pearl occupies only a small part of the giant clam shell, the "Don Gonzales Pearl" occupies almost the entirety of the shell.
2) The shell of the "Pearl of Elias" is much larger than the shell of the "Don Gonzales Pearl."
3) While the total weight of the "Pearl of Elias" and the shell is 80 kilos, the total weight of the "Don Gonzales Pearl" and its shell is only 25 kilos.
The conclusions we can derive from these observations are :-
1) The giant clam, Tridacna gigas, that produced the "Pearl of Elias" was much bigger than the giant clam that produced the "Don Gonzales Pearl."
2) Even though the total weight of the "Pearl of Elias" and its shell is greater than the total weight of the "Don Gonzales Pearl" and its shell, the size of the "Don Gonzales Pearl" appears to be much greater than that of the "Pearl of Elias"
3) Scientists believe that the smaller size of the clam is associated with the large blister pearl growing inside the clam, showing that the clam used most of its energy for the growth of the blister pearl, rather than the growth of its shell. This explains the larger size of the "Don Gonzales Pearl" compared to the size of the "Pearl of Elias." In the case of the "Pearl of Elias" the clam used most of its energy for the growth of the shell rather than the blister pearl.
4) If the approximate weight of the shell in the "Don Gonzales Pearl" is estimated between 5 to 10 kilos, the actual weight of the "Don Gonzales Pearl" lie somewhere between 15 to 20 kilos. Even if we assign 50% of the total weight of 25 kilos to the shell, i.e. 12.5 kilos, the weight of the "Don Gonzales Pearl" is 12.5 kilos, which is almost double the weight of the "Pearl of Allah."
Hence, in all probability, the weight of the "Don Gonzales" blister pearl exceeds not only the weight of the "Pearl of Allah" but also the "Pearl of Elias." Thus, assuming that no other larger Tridacna blister pearl exists in the world today, the "Don Gonzales Blister Pearl" is without any doubt the largest Tridacna blister pearl in existence.

The website of Kari Pearls - http://www.karipearls.com - give details of several other Tridacna gigas blister pearls, but none of them are as impressive as the "Pearl of Elias." One such pearl is the Diogelocas Pearl, a partially fossilized Tridacna gigas blister pearl discovered together with its partially fossilized mother shell from an eroded part of an isolated island in the middle of South China Sea, known as "Pag-asa" in the Spratly Islands, Palawan, Philippines. It appears that the Tridacna gigas giant clam was naturally buried centuries ago by the expanding island, where it was discovered. This explains the slightly fossilized appearance of both the mother shell and the blister pearl, both of which had apparently survived the long period of burial.

The blister pearl has a height of 3.75 inches and a width of 4.00 inches. In comparison the mother shell has a length of 33 inches and width of 18 inches and a thickness of 8 inches. Both the surface of the blister pearl, and the concave surface of the mother shell are slightly fossilized due to long period of burial, but have the potential of regaining their porcellaneous nature by polishing. The name Diogelocas is derived by combining the first few letters of the names of the married Philippino couple who owns the non-nacreous blister pearl.

Given below are some of the images of the Diogelocas pearl :-

1)Partially fossilized Diogelocas blister pearl and its mother shell.

2)Diogelocas pearl surrounded by the human hands giving an idea of its size.

3)Diogelocas pearl further enlarged.

Before any form of evaluation of the Don Gonzales Pearl the first step would be the examination and authentication of the blister pearl by an established and recognized gem testing laboratory, such as the GIA, GGL, AGTA, GSL etc. The Palawan Princess put up for sale at the Bonhams Natural History Auction on December 6, 2009 was examined and authenticated by gemologists of the European Gem Laboratories, USA based in New York, whose director Mitch Jacubovich commenting on the non-nacreous blister pearl, said, "This is an once-in-a-lifetime look at one of nature's most unique treasures. A pearl this size is not only one of the largest ones we have ever seen, it is among the largest pearl ever seen anywhere."

Agreed Diamanta, your suggestion is in order, and Mr. Don Gonzales is well advised to get his non-nacreous blister pearl examined and authenticated by a reputed gem laboratory before he proceeds any further.

But, what about Mr. Don Gonzales original request to assist him in not only evaluating the "pearl" but also finding a prospective customer?

I am not an authority on the evaluation of non-nacreous, blister pearls originating from the giant clam Tridacna gigas. But, I could give some useful suggestions to Mr. Don Gonzales on how to go about in the disposing of his valuable find.
Massive calcareous concretions like the "Pearl of Allah" and the "Palawan Princess" have a value of their own, not driven by any ornamental considerations, but other factors, such as :-
1) Their extreme rarity.
2) Their enormous sizes, going on record as the first and second largest natural pearls produced by a bivalve mollusk.
3) The long time taken for the pearls to develop, which may be as long as their mature life time.
4) Their natural provenance.
5) The collectors value associated with such extremely rare creations of nature, both for private collectors and well-established museums.
The most renowned of all the calcareous concretions produced by the giant clam, Tridacna gigas, is the 6.4 kg Pearl of Allah, reputed to be the largest "pearl" in the world, with staggering estimates of its value, ranging from USD 3.5 million to USD 93 million. However, the highest price ever realized by the Pearl of Allah is USD 200,000, the price paid by Peter Hoffmann and Victor Barbish, when they purchased the pearl at a public auction of the estate of its previous owner Wilburn Cobb after his death in 1980. This is indeed a realistic value of the pearl, based on which Bonhams estimated the value of the "Palawan Princess" to be between USD 300,000 to USD 400,000, when it was put up for sale at their December 6, 2009 Natural History Auction held at Los Angeles, California. In fixing this price Bonhams would have undoubtedly taken into consideration all factors that can have a bearing on the value of the pearl, such as its extreme rarity, enormous size, natural provenance, and above all the collectors value associated with it.
Based on the above observations a value of USD 500,000 would be a very realistic estimate for the "Don Gonzales Pearl" with an estimated weight of 15-20 kilos, the highest ever reported for a non-nacreous blister pearl produced by the giant clam, Tridacna gigas.
However, in disposing of the pearl, Mr. Gonzales would have to rely mainly on its collector's value, and find a suitable customer such as a renowned Natural History Museum, like the Smithsonian's National Museum of Natural History, for a privately negotiated sale. In the alternative Mr. Gonzalez could entrust his valuable find to a renowned auction house like Bonhams, who regularly conduct an annual Natural History Auction, and hopefully find a suitable customer who might be prepared to pay an enhanced price for his valuable find.