Pearl Farming is rampant around here. Back not like the white ones you get from countries like Japan.
First you get your oysters up from the depth of 6-10 meters, they're hung on buoys under the water in strings. look In them with a special tool. What they are looking for is a nice dark mother of pearl inside the oyster. The mother of pearl is what determines the final pearls colour.
At this point its time for one oyster in 30 to lay down its life. A nice coloured one gets levered open. The dark skin around the edge gets cut into 30 tiny pieces. Thirty more oysters are levered very slightly open, and a little sack at the bottom cut open, into it is inserted one of the tinny bits of the sacrificial oysters flesh and a ball made of the shell of a Mississippi clam. Why? I have no idea. I suspect its about production time. Pearls take (don't quite me on this) 18 months to 2 years to grow. If you were to put a grain of sand in there, you'd either get a very small pearl or have to wait a hell of a lot longer. The woman from the pearl farm glossed over this bit.
Pearl grows from the bit of the edge of the poor old oyster who cops it, and around the seed.
When you come to harvest the pearls, they come out in three types. Perfectly spherical pearls. Single symmetry pearls, either tear-drop or button shaped. And asymmetric pearls where there's no symmetry at all. These pearls are made into bead curtains, or thrown out. Dross.
The crap pearls are bad news for the oyster, cos there just thrown out. No good. The other oysters that have produced good pearls are re-implanted and more pearls are grown.
You can get up to 6 pearls from a single oyster, but since some don't make it, others produce pearls that are crap, eaten by turtles etc there's quite a high failure rate. The larger pearls are rarer since they have to be made using the larger, therefore older oysters - the ones that make it to the fifth or sixth pearl.
The good pearls are graded, though colour varies, its not of great importance to the value. The ones around here vary from grey to black with shades of lustrous green and purply red.
What they're graded by are imperfections, dimples, lack of lustre etc. Grade a pearls have an imperfection covering less than 5%. Judicious use of drill and mounting and that disappears.
As you go down the grades you get more imperfections and less lustre.
Low quality pearls can be quite cheap, but then you have to mount them. Good ones in nice settings are costing the blokes on this rally money that could be spent on boats.....