What causes jet black patches in SSPs?

[perlas]

I bought half a dozen pearls that are "rejects". They are baroque and very lustrous except for black "patches" in the surface making them look bi-coloured. Any ideas what causes them?

 

[perlas]

I plan to string them in a leather cord like this...

 

[lisamla]

I can't comment on the black spots, but I do think your bracelet will look very different and cool. Will you string them next to one another as shown, or spread out? I like them next to one another; looks like it will just rest across the top of the wrist.

 

[daninjt]

my understanding is the black spots are caused by bacterial infection of the saibo at the time the oyster is operated (seeded).

Cheers,

Dan

 

[CortezPearls]

Those are protein spots...the mantle has the capacity to secrete the protein conchiolin (the dark spots), calcite and nacre (aragonite)...if the oyster's hormones are acting up or if there is an infection or another "problem" (pollution, environmental change, etc.) then you will obtain those spots.

They usually crack because they easily dehydrate. Think of the shell's protein exterior...it flakes and falls from the shell when dehydrated.