Jewelry designs should most definately be copyrighted.
Intellectual property is a very serious issue.

In my previous life as an illustrator in the publishing
industry, folks thought very seriously, before infringing
directly on someone else’s work. That’s because they knew they
would be sued with breathtaking speed if they did.

It’s not about getting a profitable settlement, it’s about
changing the mentality of an industry that prefers not to be
bothered with paying for design. It took consistent, aggressive
litigation to bring the publishing industry around, and the same
will be required for the jewelry industry.