The Mineral ARAGONITE - Chemistry: CaCO3, Calcium Carbonate
...Most bivalve animals and corals secrete aragonite for their shells and pearls are composed of mostly aragonite. The pearlization and iridescent colors in sea shells such as abalone are made possible by several minute layers of aragonite. Other environments of formation include hot springs deposits, cavities in volcanic rocks, caves and mines.
And also found this:Coral Reefs Unlikely to Survive in Acid Oceans.
"About a third of the carbon dioxide put into the atmosphere is absorbed by the oceans," says Caldeira, "which helps slow greenhouse warming, but is a major pollutant of the oceans." The researchers say the absorbed CO2 produces carbonic acid - the same acid that gives soft drinks their fizz - making certain minerals called carbonate minerals dissolve more readily in seawater. This is especially true for aragonite, the mineral used by corals and many other marine organisms to grow their skeletons.
"Before the industrial revolution, over 98% of warm water coral reefs were bathed with open ocean waters 3.5 times supersaturated with aragonite, meaning that corals could easily extract it to build reefs," says Cao. "But if atmospheric CO2 stabilizes at 550 ppm -- and even that would take concerted international effort to achieve -- no existing coral reef will remain in such an environment." The chemical changes will impact some regions sooner than others. At greatest risk are the Great Barrier Reef and the Caribbean Sea....
"These changes come at a time when reefs are already stressed by climate change, overfishing, and other types of pollution," says Caldeira, "so unless we take action soon there is a very real possibility that coral reefs - and everything that depends on them -will not survive this century."
I knew about ocean acidification and problems to coral reefs - my first post was based on a LA TImes article - On "A Primeval Tide of Toxins" and the "Rise of Slime" (including the rise of jellyfish) - but somehow I missed the threat to (natural) pearls.
These days, most pearls are "fresh water pearls" - mostly made in China.
From The Culture of Freshwater Pearls:
The first cultured freshwater pearls originated in Japan. Quite soon after their initial success with cultured saltwater pearls, Japanese pearl farmers experimented with freshwater mussels in Lake Biwa, a large lake near Kyoto. Initial commercial freshwater pearl crops appeared in the 1930s. The all-nacre Biwa pearls formed in colors unseen in saltwater pearls. Almost instantly appealing, their lustre and luminescent depth rivaled naturals because they, too, were pearls throughout.
When I first visited Lake Biwa in 1973, freshwater pearl production still thrived. But, although the lake supplied most of the world's freshwater pearls, there were warning signs as development pressed toward its shores. On a return trip in 1984, I observed that Biwa's pearl farms were barely surviving, because of pollutants washing in from farms, resorts, and industries around the lake.
As Biwa production diminished, China filled the vacuum. China has all the resources that Japan lacks: a huge land mass; countless available lakes, rivers, and irrigation ditches; a limitless and pliable work force that earns less than a dollar a day; and an almost desperate need for hard currency. In 1968, with no recent history in pearling, China startled the gem world with prodigious amounts of ridiculously inexpensive pearls.
Unfortunately for China's reputation as a producer and for the impression left with the public, the initial Chinese offering, what I call the First Chinese Pearl Wave, in the 1970s and 1980s, appeared trivial. Immediately dubbed "Rice Krispies," the oddly shaped material with a crinkly surface dyed any number of "pop" colors could in no way compete with the best from Lake Biwa... Between 1984 and 1991, China learned fast and well, mastering techniques and producing better shapes and colors. Buying expertise from Japan and the U.S., the Chinese continued experimenting.
Now China is in what I call its Third Pearl Wave. Starting in the 1990s, China surprised the market with products that are revolutionizing pearling. The shapes, luster, and colors of the new Chinese production often match original Biwa quality and sometime even surpass it... China already sells round white pearls up to 7mm for perhaps a tenth the price of Japanese cultured saltwater pearls...
Once again the Chinese have radically altered freshwater culturing, making saltwater and freshwater techniques indistinguishable. They have also introduced a new type of culturing, nucleating with small tissue-nucleated pearls. Some of China's new pearls are all-nacre, some have nacre-coated nuclei, all are unmarked. After one experimenter used small off-round naturals as nuclei, he sent the resulting freshwater pearls to a gem lab and received a report identifying them as "naturals." If pearl farmers can grow cultured pearls that test as naturals, the market may be in for a wild ride.
The word "pearl" had historically meant something rare and special. They aren't so rare, now. But I still like them. And the iridescence which is part of some of the paints I use are crushed up scraps from the pearl making process.
But sea life, such as that which becomes beautiful shells washed up on the beach, will continue to have problems (if they can live at at all) without the right conditions for aragonite.
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