Thank you, I never even bothered to click that button there. Is it new? I never noticed that one before now.
That indeed is the soul mart, but the stones are stored in your inventory, accessible by your inventory bag icon. It's like a hyperlink to the inventory page. The place that you sell the stones is your inventory, not the soul mart. Hence my initial confusion. Underline, Underline, Underline, Exclaimation.