When i got my renters insurance, jewelry was not covered.
In order to get coverage for it, you needed to get a rider on the policy, which involved having the jewelry appraised, and then i believe they wanted to charge me around $20 per $1,000 appraised
depending on how much jewelry your looking to cover, it may make sense to do it this way, or to get a more expensive policy that would cover jewelery as well ( i.e without a rider for jewelry, i pay around 200/year for coverage )
that being said, i did not shop around much at the time, so i am sure there are good deals out there, but a basic policy will not cover jewelry