Rubidium is not found as a pure metal in nature because it is too reactive. Even though it is rare, it is the sixteenth most abundant element in the Earth's crust and is found in certain minerals in Russia, North America, South Africa and Canada.
Rubidium can be found on the periodic table under its atomic number 37 and its atomic weight of 85.4678. Rubidium is part of the alkali metals group on the periodic table. It can be a liquid at some temperatures, but at minus 100 degrees Celsius, it ignites in the air and reacts with water and ice. Rubidium forms alloys with cesium, sodium, gold and potassium and has a yellow, violet flame.