Hi Rudy,

This is the simplest way you can make a tapered band. There are two profiles, which are the cross-sections of the band; one at the top and one at the base of the ring circle.They are selected as profiles for a <Sweep>, using the finger circle as the rail. You can also do some other variations with two rails and scale rails which will give you more control over the shape.
For the stone mounting I also did a 1 rail sweep, sweeping a modified arc around the oval.
The resulting surface was then made solid by selecting it and clicking on <Planar>, which capped it with a top and bottom surface.
The bezel was extruded from the two inner ovals. Cap ends was checked for the extrude. The mounting base and the bezel are Boolean unioned. Then a cylinder was extruded with closed caps ,using the finger circle.(center circle)
The cylinder is Boolean subtracted from the mounting.
The top section is Boolean unioned to the band.
The connection between the stone mounting and the top of the ring was filleted a little to soften the seam.The top outer edge of the mounting base was also filleted. Since the cabochon is only for visualization purposes, I quickly made it from a solid sphere, and using the oval as a guide to shape it, I scaled the sphere with scale 1d so that it fits in the oval at it's middle. The last step is to turn on the control points of the modified sphere and move the points located below the oval curve in the front viewport until they snap into a flat surface at the level of the oval. The control points on the top of the stone can be selected all together and moved down to make the dome of the stone a bit less high. Hope this helps, If you have any questions, please ask. I'll try to post some other ways to make these rings later.

-Jesse

Note* Regarding the Boolean operations.... because the top section and the band share a coincendental curve, the Boolean blows out the inner surface, if the mounting is joined to the band before the hole is punched out of the mounting. If the bezel and mounting base are Booleaned together first, it should work fine.

Another way to make the band is a two rail sweep, using the angled side curves as rails and the cross section curves as sweep profiles.