You find ancient bone dust from some failed traps some drop them on the ground when the wrong switch is activated some spawn them in your inventory by spraying it onto the sim. Some correct activated traps will also spawn ancient bone dust around the trap, they are smaller than the one in your picture. Ancient bone dust can be found in failed and correctly activated traps either by spraying or dropping it around the traps, in dig piles both temple and jungle and in treasure chests.
There is 3 ways to cure the posion curse
1. The Statue at the market place when your on the last stage donate to the status and the curse will be done. Donate statue cost the same as the computer, but no ill side effects.
2. The computer for the Antidote for 1,000
3. Give the bone dust to 1 of the locals and they will give you an antidote, must have the poision stage two modelet for it to show up. Bonedust must be in posioned sim inventory to trade it for antidote.