Is a diamond ring essential?
The problem is that it's one of the items on the list of prescribed gifts for engaged couples, but if you think about it, the expectation for it really is a product of marketing rather than true tradition. See the article and the links in Is a diamond ring essential?
Comments
This said, it has become tradition that the ring is presented as an engagement ring and in almost all cases (as Judge Judy confirmed in US courts) the engagement ring should be returned to the groom if the wedding does not go ahead (or if the kallah pulls out in the first 6 months I suggest... )
In my personal experiences a diamond ring is so beautiful to the kallah, that it definitely helps encourage the positiveness of the marriage process :)