Few things you can do:

1. Flirting:

Wow that makes your eyes twinkle so beautifully, I could get lost looking at it

I don't know how to say this, but you wearing that necklace makes me want to divorce my wife and propose to you!!

Honestly, this might only work if you yourself look endearing/charming. If you think you don't look charming enough to pull this off, you may want to go to just regular flattery as follows.

2. Flattery:

Alright Ma'm, please just take that earring! It is on the house. That looks so good on you, I feel bad even charging you for it. [Make sure she doesn't take this seriously though!]

[A different version of the line above:] We have a special policy going on right now. You try our jewelry and the prettier you look wearing them, the bigger the discount is. Oh dear god this one has to be free! [With the perfect timing, your exclamation of something being free should be exactly when the lady puts the jewelry on. It needs to be spontaneous, not rehearsed.]

[In a low voice:] That lady over there asked me why the necklace you are wearing is prettier than the one she just bought. I told her, it is not the necklace. Its the person! [Make sure you point to a lady that you know for a fact is not with this lady though. That might not work out well for you!]

3. Provocation:

This is a bit more dangerous. Tread very carefully. Analyze your customer before you use this.

[When the customer says she wants to try a particular necklace]This one right here? I don't know.. Your skin tone does not seem to match the style of this necklace.

[When the customer says she wants to try a particular necklace]This one? Oh this is on the expensive side. This comes out to be $350. Do you still want to try it on?

[When the customer tries a particular necklace]I feel like you may need to go for something more [random necklace lingo].

4. Brutal honesty:

By brutal honesty, I am not suggesting telling the truth. I am suggesting telling lines that sound like there is no need for you to lie about them.

Of all the necklaces we have, this is the one necklace that is actually worth the price. I barely make a profit from this one piece right here. I sell it for its beauty and nothing else.

I got to be honest, I know this is overpriced. I am not going to act like this is cheap. But this one has a lifetime warranty and you cannot find any that looks as pretty as these ones. You can go over to [some other jewelry store] and see how much they charge for the stuff they sell. And compare the quality of the two.

You got to agree that is prettiest thing you've seen! I know it is pricey, but just look at yourself! You got to agree you love how radiant you look right now.

Conclusion:

Obviously, I do not know ANYTHING about jewelry. Its not about what you sell, its about how you sell it. This is what you are hoping to achieve by using these lines:

1. Make the customer laugh.
2. Make the customer talk.
3. Make the customer stay.
4. Make the customer like you.

All these are going to give you an advantage and maybe help you make a few more sales.

Disclaimer:

I do not have any sales education. I've worked a few jobs in sales, but nothing commission based (where making sales was a priority). I've just heard a lot of people tell me I have a way with customers. That is where all this is coming from. If any of this is stupid or wouldn't work, please let me know in the comments. I'd love to learn why I'm wrong.

I hope this helps you close more sales.