MOP is nacre. Same nacre as in a round pearl - when an oyster creates a pearl the interior of the oyster's shell is coated with the same exact nacre as the pearl is formed with. GMOP comes from Tahitian pearl oyster shells. For ~18 months the oyster deposits layer after layer of nacre, thousands of layers, each layer maybe a half micron thick... It's all very romantic.
GMOP gets its iridescence in two ways -
1. Nacre is translucent. So when light hits a slab of MOP (or a pearl's surface) the light actually goes nto the nacre. And it bounces around between the nacre layers for a bit and eventually leaves the MOP, and that's what your eyes see. Areas where those nacre layers are thinner or thicker will show different iridescence colours because of the differences in how those layers play with light.
2. Nacre is "textured". Those "growth lines" that all GMOP has, that's the nacre forming unevenly, probably over artefacts in the shell that we can't see because the shell is gone. Some oyster species also just tend to create more nacre surface #stuff than others - WMOP (from South Sea pearl oysters) is often a lot "smoother" than GMOP, for example. The "growth lines" create hotspots for really varied light interference - GMOP with more "texture" will also be more iridescent, generally.
#1 looks more textured to me. #2 looks less textured. So #1 is my pick. Can't judge for sure via photos but the couple you've got support expectations.
GMOP gets its iridescence in two ways -
1. Nacre is translucent. So when light hits a slab of MOP (or a pearl's surface) the light actually goes nto the nacre. And it bounces around between the nacre layers for a bit and eventually leaves the MOP, and that's what your eyes see. Areas where those nacre layers are thinner or thicker will show different iridescence colours because of the differences in how those layers play with light.
2. Nacre is "textured". Those "growth lines" that all GMOP has, that's the nacre forming unevenly, probably over artefacts in the shell that we can't see because the shell is gone. Some oyster species also just tend to create more nacre surface #stuff than others - WMOP (from South Sea pearl oysters) is often a lot "smoother" than GMOP, for example. The "growth lines" create hotspots for really varied light interference - GMOP with more "texture" will also be more iridescent, generally.
#1 looks more textured to me. #2 looks less textured. So #1 is my pick. Can't judge for sure via photos but the couple you've got support expectations.
