One element probably worth mentioning here: Iridium.
While iridium is actually fairly common in the whole of the Earth, it's exceptionally rare to find it in Earth's crust; by comparison, gold is about 40 times more common. There are two reasons for this:
- Iridium is one of the very densest elements (basically tied with Osmium), so it tends to sink.
- Iridium is a "siderophile" element, so it easily dissolves in liquid iron.
The combination of these two things means that when Earth was forming, heating, and differentiating, almost all of the original iridium sank deep down into Earth's liquid iron core, and has been locked away there to this day.
In general, if you find iridium at the surface, it almost always came later from a meteorite impact. In fact, it's a very reliable indicator of past impacts: there's a clear iridium-rich layer of rock right at the K-T boundary, the impact responsible for wiping out the dinosaurs.