OK we know that the dog will go out and find it for you but it's a lot of work. What I've found is that you can bring the Tiberium to your house!!! Just start researching Science and not long after you'll find a 'Group Science Project' in your family inventory. Drag it out of inventory and place it anywhere on your lot- just a side note and not crucial but you might want to put a fence around it so that random nerds from the neighborhood don't come and mess with it while you're using it. (Personally I like to use half walls because it's easier to look for rocks on the floor if you can put all the walls down, I just remove 1 or 2 panels and use a fence with a gate in the open area)
One sim can do this all on their own, you might get different outcomes the first few tries but once you're used to it, it's really easy...well so long as you pay close attention. Once you're set up click on the project and have all 3 actions lined up- and start the actions. At the top of the science project there will be a light indicator that shows your 'progress' once you start....when the meter gets to about 33% (jumps twice) stop the first action and move on to the second, when that jumps to around 60% (jumps twice again and begins to turn green) stop that action and move to the third until it ends automatically. (using 1 or 2 speed is best, but I've never gotten the meteor shower with speed 3)
Once you have auto stopped the third command click on the science project again and a single action will be available 'Pull lever of Doom'. Go ahead and press it. The color of the light emanating from the machine SHOULD be white- that will trigger the meteor shower of collectables. IF it's pink you'll get a uninhibited moodlet that doesn't really do anything to you. IF it's blue everyone on the lot will be instantly knocked out for a 'power nap' (this includes visitor and zombies). Once you pull the lever you'll see giant water drop things falling from the sky- that will be the collectables. You can go ahead and pick them up or do the machine a few more times and collect them all at once. You CAN collect the first batch with a second sim while your first sim works the machine again- just MAKE SURE to pause it a lot and watch that light meter on the Science project, but I've just found it easier to do it after running the machine a few times and use both sims going in different directions to pick up the items.
You can get ALL high level items- from Tiberium to Soul Peace. There is no way to know what you'll get but considering you can do this repeatedly without leaving your own lot...it's much easier then searching for it. Also investing in a gem cutting machine will also help since you'll be collecting enough gems to keep you busy for days cutting them...and you can cut entire stacks with one click and no fee. One side note is to consign all your Tiberium!! After aging the gems can get to over $40,000 EACH but if you sell it at the consignment store you'll sell them for $60,000+ each! Just make sure to cut all your lesser gems first to unlock the spiral cut before you cut the Tiberium. I'm not sure when that unlocks but I know the normal top gem cut opens up after 100...and you get to spiral cut Tiberium way before that.
OH forgot to add- make sure to 'grow' all the gem dust you get from Tiberium as well....they will also grow into spiral cut large gems without doing anything more. So for each uncut Tiberium you'll get at least 4 spiral cuts at $60,000 a pop.
