Cut diamond rings are rings that contain cut (as opposed to raw) diamonds. Nearly all diamond rings have cut diamonds on them. Diamonds, when first mined out of the earth, are considered "raw" and don't look particularly interesting. To bring out the "fire" and beauty that people associate with diamonds, it's necessary to cut the diamonds. This involves shaving off pieces of the diamond and cutting facets that bring out its shine and brilliance. A cut diamond will often be a great deal smaller than a raw diamond but it sells for a good deal more. The lowest quality diamonds (those with large, visible flaws), furthermore, are almost never selected for cutting or placement on jewelry rings but, instead, are used for a variety of industrial applications.