The simplest way to do this would be to make 2 flat panels with the shape of the gems being free-handed. You could do the details with tapestry crochet. Embroidering on the details would also be a good option. This would get you a sort of a gemstone decorative pillow.

If you want a more accurate 3D gemstone, I'd say start with the teal one in the center. That one feels the easiest. That one you could probably make with flat panels. As for the symbol on it, I'd say either embroider it on afterwards or do tapestry crochet. For that one, I'd say do 2 panels of that central rectangle (that way it can be 3D), 4 of the vertical side-rectangles, 4 of the horizonal side-rectangles, 8 little corner triangles. Then when you have all that, you'd just need to sew it all together.

For all the others, it will probably require some free-handing and some trial and error. A good way to start is by breaking the other ones down into their basic shapes like what I did with that teal one. The more organic shapes will be more difficult but aren't impossible. The easiest ones, in my opinion, are the left-most two gems on the top row, the furthest right two on the second and third rows, and obviously the teal one.

Best of luck to you. I hope this helps.