It looks like a hard, green crystal and emits black smoke when in contact with flame. Smelling it a little is good for body and spirit, totally breathing it in properly fucks you up. The first few days you'll feel like you don't get tired, no hunger, no thirst. If you just smelled a little, that's it. Thus it can be good if your gonna spend some time without food or water. Within 2-3 days, you'll be human again with hunger and thirst. If you smelled a lot, you'll continue to not feel hunger or thirst. After maybe two nights, you'll feel horrible. If you eat or drink anything, you'll throw up. A bit of fruit? Vomit. Some rice? Vomit. A small cup of water? Vomit. Body and head pain and constant diarrhea is a nice bonus too.
Your vomit will be green and filled with bile. If you just smelled a little you sometimes cleanse your gallbladder regurgitate a bit of bile. Too much black smoke and you vomit maybe 100ml of it at a time.
The only thing I know that you can drink without trowing up is coconut-water, but even that only in too small sips to suvive more than a two weeks.
The way I got the poison to pass was cooling myself off by bathing in the river at night. It's not really considered a poison, since it's not in small doses. The actual poisons are a bit more painful or otherwise horrendous.