While searching for something completely different (The Cathedral Effect), I stumbled upon this blog by the Lauren B company. I has an incredible wealth of information in that blog about jewelry. It is very thoroughly done and nicely written. I have no interest whatsoever in jewelry, but this blog is really good.
How I stumbled upon this blog: there is a concept in jewelry for engagement rings called Cathedral Style Engagement Ring Setting. See this post. Geeky details, lovely