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== Occurrence ==
This element is considered to be the 16th most abundant element in the [[earth]]'s crust. It occurs naturally in in the minerals [[leucite]], [[pollucite]], and [[zinnwaldite]], which contains traces of up to 1% of its [[oxide]]. [[Lepidolite]] contains 1.5% rubidium and this is the commercial source of the element. Some [[potassium]] minerals and potassium [[chloride]]s also contain the element in commercially significant amounts. One notable source is also in the extensive deposits of [[pollucite]] at [[Bernic Lake]], [[Manitoba]].
Rubidium metal can be produced by [[reduction|reducing]] rubidium chloride with [[calcium]] among other methods. Rubidium forms four oxides: Rb<sub>2</sub>[[oxygen|O]], Rb<sub>2</sub>O<sub>2</sub>, Rb<sub>2</sub>O<sub>3</sub>, Rb<sub>2</sub>O<sub>4</sub>. In 1997 the cost of this metal in small quantities was about [[US dollar|US$]] 25/[[gram (unit)|gram]].
== Isotopes ==
There are 24 [[isotope]]s of rubidium known with naturally occurring rubidium being composed of just two isotopes; Rb-85 (72.2%) and the [[radioactive]] Rb-87 (27.8%). Normal mixes of rubidium are radioactive enough to expose [[photographic film]] in approximetely 30 to 60 days.
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