To model a gemstone, start with a solid mass, and cut away the facets, one by one, by boolean, using a cutting object of the proper shape. Rotate the tool around the centerpoint, for each cut. A different cutting tool for each type of scalloped cut?
If the glass is smooth inside, revolve vertical profile U curve, for the inside, with an angled vertical line for the outside, to make a truncated cone cup starting solid.
It is hard to tell from the picture, the geometry.
- Brian

A mold may have been used for the original?
Array and shell come to mind?
Is the glass partly square?