Question

Is rubidium man-made or natural?

Answer 1

1. Rubidium can be found in nature in the minerals leucite, pollucite, carnallite, and zinnwaldite, which all contain up to 1% rubidium oxide.
2. Rubidium is a silvery-white, extremely soft metal that is one of the periodic table's most reactive elements.

Hence, rubidium is natural, not man-made.