It wasn't until the early 20th century that diamond wedding rings became popular. During the 1920's, diamond wedding bands were marketed as a way to symbolize the enduring nature of love and marriage. Today, some type of diamond wedding band is now the predominant style for couples.

No, a women's wedding ring does not HAVE to have diamonds or gemstones. The tradition of a diamond wedding band is still a relatively newer one. Many women still opt for a simpler traditional plain precious metal wedding band without any type of diamonds at all. Ultimately, the choice of wedding ring style is a personal one.

Diamond wedding rings, or wedding rings in general, are worn on the fourth finger of the left hand, known as the "vein of love" traditionally believed to be directly connected to the heart. Now different countries and customs do where the wedding ring on a different finger and hand entirely, such as in Russia, Germany, and India (worn on the right hand instead).

As long as there is at least a portion of the diamond wedding ring exposed with just precious metal then yes, diamond wedding rings can be resized. Some intricate designs and eternity rings (where the diamonds extend the entirety of the ring) are very difficult if not impossible to resize.