So you've made a very significant purchase and now you want to insure it. So, the steps to insure and engagement ring are the following. You can inquire with your renter's or homeowner's insurance, see if you can put a special rider on your ring or you can contact an individual insurance company and get a policy just for that stone. You're going to need two things in order to insure your ring. You need the GIA Certificate which hopefully came with your ring that gives your stone's identity and it describes the quality of the stone and you also need an appraisal which will put a monetary value on your stone.
Also if your diamond gets lost of stolen, you'll be able to easily replace it if the insurance company has the information on your original stone. Not everyone chooses to insure their diamond ring. That's fine. Just know that accidents do happen and sometimes stones fall out. You've made a significant investment. Protect it by getting some insurance.