Within two years of the invention the authors announced the discovery of two metals, rubidium and caesium, closely allied to sodium, potassium and lithium in properties, in the mineral lepidolite and in the Diirkheim mineral water.
The angle between the optic axes varies from 70 0 -50° in muscovite and lepidolite to Io - o° in biotite and phlogopite; the latter are thus frequently practically uniaxial.
To the first class, with the optic axial plane perpendicular to the plane of symmetry, belong muscovite, lepidolite, paragonite, and a rare variety of biotite called anomite; the second class includes zinnwaldite, phlogopite, lepidomelane and most biotites.
The species lepidolite is largely used for the manufacture of lithium and rubidium salts.
Klaproth had discovered the presence of potassium in leucite and lepidolite, it occurred to L.
News, 1864, 10, p. 181), and, associated with rubidium, at Diirkheim; it is also found in lepidolite, leucite, petalite, triphylline and in the carnallite from Stassfurt.
It is found in the minerals lepidolite, petalite and in various specimens of mica and of carnallite, and in some mineral waters.
The best source of rubidium salts is the residue left after extracting lithium salts from lepidolite, the method of separation being based on the different solubilities of the platino-chlorides of potassium, rubidium and caesium in water (R.
It is only found in combination, and is a constituent of the minerals petalite, triphyline, spodumene and lepidolite or lithia mica.
It may be obtained (in the form of its chloride) by fusing lepidolite with a mixture of barium carbonate and sulphate, and potassium sulphate (L.