I Believe these to be Naturals. :)

[Casey.R]

Bodecia I can see why you thought they might be naturals, something about the shape, and of course the clasp is old.
Caitlin, your a very lucky woman. Those are beautiful and of course so unusual. I like your friends mixed strand too. Where are those from?
Valeria, thanks for posting a link to that cool site.

 

[GemGeek]

Caitlin showed a terrific example of where at the drill hole, the nacre had peeled, but there was still a pearly layer underneath. Natural pearls with exhibit lustre even where they show wear, although it's possible to get a little variation in lustre.

If you have dead-looking pearls in the strand, they have lost their coating of nacre. If you are going to crack a pearl in half to see if it has a coating, you need to crack a good one. Even then, the layer may be very thin and just flake off.

If I had a kid, this would make a good science fair experiment.

 

[Caitlin]

I can see why you thought they might be naturals, something about the shape,

If you are not used to old baroque akoyas, one might think their shapes are natural . A giveway on baroque akoyas is how the nacre piles up . The way it piles up is fairly typical of baroque akoyas. or as Val101 says :

Here the pearls are not perfectly round, but the variation of the shapes is more in line with defects of cultured nucleated pearls.

Next time you see those shapes, you will recognize them as baroque akoyas

 

[Caitlin]

Sometimes new naturals are more expensive then the old

I think you are right. If you want round natural strands, you must go old, and the prices are climbing. I have never seen a baroque necklace in the sizes we are talking about and I couldn't find one, so,,,
Here is a picture of the typical shapes of old, round, naturals. They are more like barrels.