Freshwater Pearls versus Saltwater Pearls
At The Pearl Girls we absolutely love freshwater pearls. Although we use some saltwater pearls in our pieces, we love freshwater because they are the closest rival to natural pearls. I know that some people misunderstand freshwater pearls. After Mikimoto started culturing saltwater pearls in the early 1900s, he tried the same process in freshwater yet he could not produce gem quality pearls! The freshwater pearls looked wompy. "Huh?" you might ask. Wompy is the very professional term I use to describe a pearl that is just a little off. In this case, these Japanese pearls were not quite so round, they had a funny surface quality and, in some cases, the Biwa pearls looked like pieces of rice. So, the name freshwater pearls became synonymous with off sized, lower quality pearls.
Here are some examples of larger Biwa pearls from Japan. They have an absolutely amazing luster yet they were not the same gem quality pearls (meaning they were not as round!) as the pearls being cultured in saltwater!
World War II halted the efforts to culture freshwater pearls in Japan. As you might imagine the lakes region was devastated. Overall devastation, destruction and pollution made Lake Biwa a non-factor after the war. And, as for the saltwater pearl industry, it was also devastated. I recently learned that American soldiers worked at the Mikimoto pearl farm after the war. A vet named George H. told me, "I was one of the American soldiers that worked at the farm in Ago Bay back in 1948-1950 before going to Korea with the 27th Wolfhonds in July 1950." So interesting!
Freshwater Pearls on the Rise
So, the freshwater pearl production in Japan was over but, the spirit behind culturing pearls in freshwater did not die. Inspiration just moved on and the Chinese took over perfecting this process of culturing pearls in freshwater. They have come leaps and bounds in the past decades producing large, beautiful and round freshwater pearls. Suddenly, freshwater pearls develop into some very high quality, beautiful pearls.
So, what is the difference in freshwater and saltwater pearls? To answer this, we turn to Pearls: A Natural History which was a huge exhibit on pearls at the American Museum of Natural History. Unfortunately, this exhibit is no longer available but the book from the exhibit remains one of my valuable resources. I have also included other information from my studies in this comparison...
What is in a Pearl?
The composition of saltwater and freshwater cultured pearls are almost the same. So, there is no difference in the actual pearl making material. I love this idea because when people try to argue that a saltwater pearl might be more valuable than a freshwater pearl, the value would not reside in the chemical makeup of the pearl. The only difference is that freshwater pearls have a higher amount of the mineral manganese. However, both types of pearls are made of calcium because it is the same material of the mollusk's shell. A mollusk uses its same shell making nacre to make a pearl so pearls are primarily calcium.
The composition of a freshwater pearl is very different from a saltwater pearl. Saltwater pearls have a bead nucleus. This means, at the center of a saltwater pearl is a mother-of-pearl bead inserted by the grafter to start the pearl making process. Freshwater pearls do not have a bead in their center. So, freshwater pearls are closer to natural pearls in their composition. They also are heavier since the pearl is heavier without a mother of pearl bead in the center.
The saltwater pearl environment in primarily water based while the freshwater pearl environment is primarily land based. This makes a huge difference in terms of access and money! It is more expensive to have an ocean based operation that relies on a staff in a remote location working off of boats. So, the upfront costs of culturing pearls in saltwater are higher than culturing pearls in freshwater.
Here I am on my way to a freshwater pearl farm (row, row, row your boat) in China.
And here I am heading off to an ocean based operation in Fiji.
This may not seem to be a huge difference and yet, imagine paying your staff to live on an island, in a remote location and rely on ocean based boats to access your oysters. Imagine the problem with the threat of theft, diseases or ocean based natural occurrences including typhoons and red tide. Freshwater lakes do not pose the same risks that oceans do.
In the ocean, your wild stock of baby oysters can float out to sea with the tides. The truth is an ocean based operation costs a lot of money. In fact, when I visited this pearl farm in Fiji, the owner said he did not even make money until his second seeding of the oysters. So, his entire first harvest went just to breaking even. And this was on pearls that cost up to $500 or more a piece!!
The Process of Culturing Pearls
There is also a difference in the process of culturing pearls in freshwater versus saltwater. First, freshwater mussels larvae has a different growth trajectory than oyster larvae. Freshwater mussel larvae attach to a fish host before they metamorphose into juvenile mussels. It is a unique relationship between the fish and the mussel. This means, to breed and grow mussels to eventually culture pearls in, the hatcheries must culture fish as well.
Saltwater spats (baby oysters) do not rely on a fish host but they are susceptible to being washed out to sea, or being eaten by mature oysters. So spat must be carefully nurtured as well. They are collected and offered something to attach to when they are mature enough. Again these juveniles must be cared for years before they ever culture a pearl.
Where the Pearl is Born
Inside the saltwater oyster or the freshwater mussel, the placement of the nucleus is different. In saltwater pearls, a bead or shell is inserted in the gonad of the oyster. What is a gonad? The sex gland. It is easy to access in the oyster so it makes a prime placement for the nucleus of the oyster. Check out my video of a grafter nucleating a saltwater akoya oyster.
In freshwater mollusks a small piece of tissue is placed in the soft mantle tissue which lines the shell. A piece of shell would never fit in this thin lining so a piece of tissue is used instead. This leads to our third difference..
How Many Pearls?
There are ALOT more pearls in a freshwater mollusk than there are in a saltwater oyster!
I hope this helps you understand the differences in these pearl processes.