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

Don Gonzales from the Philippines uploading a post on to the Internet Stones.COM Media facebook page on March 23, 2013, reports of the discovery of an extraordinarily large non-nacreous pearl weighing 25kg from the giant clam Tridacna gigas, found in the waters off the coast of Philippines. Several such discoveries of massive calcareous pearls from the giant clam have been reported before from the waters of the South China Sea off the coast of Philippines, particularly from the Island of Palawan. One such famous pearl is the "Pearl of Allah" weighing 6.1kg, believed to be one of the largest "pearls" in the world, and discovered in 1934.
This is what Don Gonzalez has to say about this latest discovery :-

Gentlemen,
We are in possession of a "non-nacreous pearl" (as shown in the attached images) weighing approximately 25kg, including the weight of one valve of the clam. It is similar to the "Pearl of Allah, also known as the Pearl of Lao Tzu or the Pearl of Lao Tse".

Can you please gentlemen assist us on how we can evaluate and sell this pearl to a prospective customer.

Thank You.

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.

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.

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.