An example of a combination saw and cabbing machine
Cabbing, the making of cabochons, is generally limited to translucent and opaque gemstones. Think of gems like lapis, jadeite, star sapphire, etc. However it is not specifically limited to these types of gems. One of the most famous jewelry makers in the world, Bulgari, is renowned for it’s cabochons of transparent gems. That said, most transparent gems of high quality are faceted for a number of reasons.
A round cabochon cut sapphire
The only reflection is from the surface, no scintillation, no sparkle