About Natural Pearls - Natural Sea Pearls

Natural pearls are nearly 100% calcium carbonate and conchiolin
It is thought that natural pearls form under a set of accidental conditions when a microscopic intruder or parasite enters a bivalve mollusk, and settles inside the shell
The mollusk, being irritated by the intruder, forms a pearl sac of external mantle tissue cells and secretes the calcium carbonate and conchiolin to cover the irritant
This secretion process is repeated many times, thus producing a pearl
Natural pearls come in many shapes, with perfectly round ones being comparatively rare
Typically the build up of a natural pearl consists of a brown central zone formed by columnar calcium carbonate (usually calcite, sometimes columnar aragonite) and a yellowish to white outer zone consisting of nacre (tabular aragonite)
The presence of columnar calcium carbonate rich in organic material indicates juvenile mantel tissue that formed during the early stage of pearl development
The fragile rim of the shell is exposed and is prone to damage and injury
Crabs, other predators and parasites such as worm larvae may produce traumatic attacks and cause injuries in which some external mantle tissue cells are disconnected from their layer
Embedded in the conjunctive tissue of the mantel, these cells may survive and form a small pocket in which they continue to secrete their natural product: calcium carbonate
The pocket is called a pearl sack, and grows with time by cell division; in this way the pearl grows also
With ongoing time the external mantle cells of the pearl sack proceed to the formation of tabular aragonite
When the transition to nacre secretion occurs, the brown pebble becomes covered with a nacreous coating
As this process progresses, the shell itself grows, and the pearl sack seems to travel into the shell
However, it actually stays in its original relative position within the mantle tissue
After a couple of years, a pearl will have formed and the shell might be found by a lucky pearl fisherman
Value of a na tural pearl
Quality natural pearls are very rare jewels
The actual value of a natural pearl is determined in the same way as it would be for other “precious” gems
The valuation factors include size, shape, quality of surface, orient and luster
Single natural pearls are often sold as a collector’s item, or set as centerpieces in unique jewelry
Very few matched strands of natural pearls exist, and those that do often sell for hundreds of thousands of dollars
In 1917, jeweler Pierre Cartier purchased the Fifth Avenue mansion that is now the New York Cartier store in exchange for a matched, double strand of natural pearls that he had been collecting for years; valued at the time at $1 million USD