mine is as a separate part of my homeowners insurance through travelers. it costs me like $120 for the year with a $500 deductible for $21,500 of coverage (the appraised value of my ring - dang thing appraises higher and higher every year which just makes the insurance more, oh well, I love it no matter what), full replacement including if I lost it (not all policies will cover loss or damage (I had a friend chip her tiffany diamond in the dryer and her policy replaced it completely, some only cover theft)
you will have to have it professionally appraised, but that's no big deal. get it insured ASAP!
Why was her ring in the dryer?