I have a 2 straded choker pearl necklace around 9mm with a 14kt white gold clasp w/ safety catch with 4-ribbon bow design and 7 diamonds and tiny diamonds along perimeter of each bow. I bought the necklace second hand so I know nothing about it except the pearls have a lovely luster and ivory color. they were very dirty and some near clasp were discolored yellowish-green. I used a damp cloth to clean pearls and remove discoloration. There are no maker's marks on the clasp. I'm not sure what kind of pearls I have. How can I tell?