Actually, I just realized how stupid the Lunarians are for not swiping Cinnabar at the very first opportunity. As far as I know, she is the only gem that generates any material at all. Every other gem, including the top dollar ones like Dia and Phos may be incredibly valuable upon acquisition, but they can no longer generate additional value above that after they are already processed into jewelry, machines, etc.
Cinnabar, however, seems to be valuable not as a commodity, but a source, for (possibly) unlimited amounts of Mercury.
So basically, your favorite gem a shit and Cinnabar is most valuable gem and only intelligent and business-minded anons can truly appreciate her worth..