Tunde, here is a shot taken quickly at work today..I guess the boss thought I was "learning". Maybe I really was. : )

The idea is to show reflections and getting rid of or controlling that.  Pay no attention to color or other stuff since none has been touched to make a decent shot. And, lighting is all wrong for the gemstones, no life there.

See the black reflection in the image on the left?  I took a piece of white copy paper, rolled it up a bit and moved it around to see how reflection was affected. I suppose the ring gained some light from the white paper but also the paper reflected in the ring and between the ring and the cause of the black dead area.  This is what I mean by "set-up" is 90% of the time.  It takes a while and some test shots to see if our eyes are telling us what is really seen in the camera!

A simple move of the paper and the black went away.   Now, there is reflection above that...well, no need to do this ring anymore!  I hope the pics help you understand what I am getting at.

A paper or object can act as a relfector of light, as a gobo(go-between) blocking light and casting a shadow, or can be reflected in the metal itself and be unobtrusive.   Obvioiusly if a red paper was used in this case, the ring would have shown an unnatural red area...so white was chosen to match the background.          Take care and have fun with your light tent!               Tom.