I loosely arranged tehm around the existing gem values, but these new ones are mostly lower value than the existing ones. At the low end, jetstone is still several times as dense as silver by value/weight ratio, and at the high end, topaz fits between emerald and amethyst.
Note that the artwork is not strongly compressed, since I hope someone will either improve or replace it with better artwork. This artwork is all submitted as CC BY-SA 4.0.
In one case I included an .xcf file which is the Gimp original. For the others, I included .pxo files, which are from the Pixelorama image editor. If you change or replace the artwork, please either update or remove these originals.
DraugTheWhopper