It's considered a gem and it's generally found in China. However, the easiest way to get it on a regular basis is to have your Sim train to become a martial arts expert. It's one of the gems which comes out of the space rock block on the block breaking item (which you can get from buydebug under misc.)
Not sure if Tiberium is found naturally in China or in Egypt, but my most common way of getting it is having a disciplined martial artist who's completed the timber breaker martial arts challenge break space rock boards for it.
Edit: out of the gem/rock spawners in buydebug, I believe it's listed as an egyptian spawner.
This message was edited 1 time. Last update was at 06/10/12 10:04 PM