Pearls - saltwater?

Picked up these pearls for £1 today at the car boot sale mainly for the Sterling clasp but when I looked under a loupe I'm almost certain they are real as they have that pinky lustre and slightly irregular surface. I think they have been restrung without knots and very tightly as they are kinked. The clasp may or may not be contemporary.
Some questions- I'm not tooth testing until washed as they are VERY dirty- can I just use a little dish soap?. I'm going to restring them but I need to keep them in order so I don't have to faff about graduating them.
Presuming these are real, being very round are they likely saltwater?. No rings or ridges round the middles.
Lastly, one has a small area where the top layer has been chipped. It doesn't look like glass etc underneath but do pearls have nacre in layers?
Thanks for looking.

 

yes

yes

 

Definitely a home stringing job. Really pretty clasp.

 

Thankyou. Are they likely saltwater as so round? I struggle to know how people identify the different types of salt water pearls and the good or outstanding from the indifferent. I think I've got the qualities of freshwater more sorted now but I've got several strands of nice round presumably salt water ones that are still a bit of a mystery.

 

Fist clean them up so you can tooth test.

 

I am pouting at the thought of a car boot sale.

 

Will do tomorrow

Haha, to be honest it was pretty rubbish but it was SO good to be out. First time since mid march I have been anywhere other than a food shop or to work. Which county are you in OBB? We aren't too bad for CV in Gloucestershire but Somerset has been very hard hit and I think some counties up north.

 

Couldn't wait so gave them a quick wash and definitely gritty!. The real thing

 

Cultured pearls then. Need restringing with knots between.