These are meteorites, space rocks that have fallen from the heavens. They come in three varieties: Tiny, Large and Gigantic 2x3 Space Rock (spotted via the telescope using 'Search Galaxy', there will be a message telling the player that a Sim has seen it and where it is on map view) it is also possible to find gigantic space rocks in trash cans. Initial appraisal appears to be based on their weight, so naturally Large Space Rocks are worth more than Tiny Space Rocks. However, a Sim may Analyze a space rock, which will result in it being one of the below types. Each type may be worth more or less than initial appraisal. Finding half the rocks makes it easier to find the other half, and finding all the rocks results in finding the more expensive ones more often.
Rocks can be found using the "Rocks and Gems" setting on the Collection Helper. A Sim may also spot a meteor falling while using the telescope, which will mark its position on the map. Sometimes when buying a house an event will pop up that the house the player purchased was struck by a meteor, and ask to accept the challenge. Doing so results in several Large Space Rocks and Tiny Space Rocks scattering the home (along with fire damage).
If World Adventures is installed, Sims with a high enough Martial Arts skill can break these rocks on a board to reveal random gems. In addition to the normal gems, space rocks may very rarely contain Tiberium (from the Command and Conquer series). Tiberium has a unique cut (Spire Cut) that allows it to glow in the dark, but keeping it in a Sim's inventory will make the Sim nauseous.
If the Ambitions is installed, there is also a very small chance of Meteories falling near/on your sim. You will be given a warning - "<Sim> wonders why it suddenly got so dark" - and if your sim doesn't move, He/she will crushed under the falling meteor. However, if the Sim does not get hit, one Gigantic and several Large Space Rocks will be strewn over the crash site.
|Acapulcoite||Gigantic, Large & Tiny||70%|
|Angrite||Large & Tiny||100%|
|Ataxite||Gigantic, Large & Tiny||150%|
|Aubrite||Large & Tiny||140%|
|Brachinite||Large & Tiny||120%|
|Charbonaceous Chondrite||Gigantic, Large & Tiny||500%|
|Chassignite||Gigantic, Large & Tiny||120%|
|Diogenite||Large & Tiny||90%|
|Enstatite Chondrite||Gigantic, Large & Tiny||600%|
|Eucrite||Large & Tiny||80%|
|Hexahedrite||Gigantic, Large & Tiny||160%|
|Howardite||Large & Tiny||70%|
|Kamasite||Large & Tiny||175%|
|Lodranite||Large & Tiny||80%|
|Lunar||Large & Tiny||130%|
|Mesosiderite||Gigantic, Large & Tiny||1000%|
|Nakhlite||Large & Tiny||110%|
|Octahedrite||Gigantic, Large & Tiny||180%|
|Ordinary Chondrite||Large & Tiny||50%|
|Pallasite||Gigantic, Large & Tiny||400%|
|Rumurutite||Large & Tiny||300%|
Gigantic, Large & Tiny
|Unusual Bellacite||Gigantic, Large & Tiny||160%|
|Unusual Custerous Gossticite||Gigantic, Large & Tiny||190%|
|Unusual Dukeadite||Large & Tiny||220%|
|Unusual Holmberic||Large & Tiny||180%|
|Unusual Llamatite||Gigantic, Large & Tiny||200%|
|Unusual Mazzadrayte||Large & Tiny||210%|
|Unusual Pearsonite||Gigantic, Large & Tiny||210%|
|Unusual Rodiekceous||Gigantic, Large & Tiny||200%|
|Unusual Sporecite||Gigantic, Large & Tiny||170%|
|Ureilite||Gigantic, Large & Tiny||90%|
|Winonaite||Large & Tiny||130%|
If The Sims 3: Seasons is installed, Aliens can transmute space rocks to get brain power. The bigger the space rock the bigger the amount of brain power the alien gets. Aliens can also summon them which will almost empty their brain power.