Okay, so I found Tiberium on ground in Egypt by the southern beach area(?). Anyway, was very excited, sim got home and I put the 2 pieces out in the garden and so far it's been a week and not a thing has happened.
You mean that it doesn't turn into a crystal?
What I have found is this:
I put the Tiberium in the Sims inventory and nothing happens. I put the Tiberium on the ground and still nothing happens. I put it in inventory and
travel and within a few hours of arriving at the new destination the Sim will get the nausea. Then I put it on the ground and within a day or so it will turn into the 40.000 simoleon crystal.
There are only a few times where this hasn't happened, maybe I found the Tiberium immediately before traveling? You can see it's about to turn when it shoots green sparks, if it doesn't do that nothing will happen. Then I put it back in inventory and the next times she travels it turns. I've never sent it to the gem cutter because I'm cheap and it will happen on it's own.
I have yet to see it spawn new Tiberium though, maybe I haven't waited long enough.