Vol. 5 6. J OF MINERALS CONTAINING RARE ELEMENTS. 527 



•quarries near Moss, and was described by Blomstrand under the 

 name of broggerite. We have here a remarkable mineral, the 

 commonest (not thoria-bearing) variety of which already many 

 hundred years ago attracted the attention of the miners and metal- 

 lurgists of Saxony, and proved the source of much trouble to them. 

 It was a black mineral, heavier than any other in the earth's crust 

 except the native metals. Prom its weight the miners concluded 

 that it must contain a metal, perhaps gold, the heaviest that they 

 knew. All their attempts, however, to obtain the metal from this 

 ore, either by fire or by corrosive liquids, proved total failures. The 

 -old miners held it to be a spell-bound ore, changed into worthless 

 rock by malevolent gnomes, and they contemptuously gave it the 

 name of pecherz. Only a cenfcuy ago Klaproth succeeded in 

 isolating from this enchanted ore a new element, which he called 

 uranium after the planet Uranus, discovered a short time before 

 by Herschel. The name reminds us also of the belief, prevailing 

 up till the middle of the eighteenth century, that the number of 

 planets in our solar system corresponds with the number of metals 

 in the earth's crust. 



A remarkable gap in the chemical system was thus filled, and 

 the use of uranium-preparations in porcelain- and glass-manu- 

 facture, in photography, and as chemical reagents, has gradually 

 become so widely extended that <£50,000 worth or more of uranium- 

 minerals is consumed every year. The only localities from which 

 uranium-ore has hitherto been obtained in fairly large quantity 

 are the Cornish tin-mines and those in the border-districts of Saxony 

 and Bohemia. Uranium-minerals are obtained in smaller quantity 

 from several other localities. Sweden, however, is the fortunate 

 possessor of the largest, though as yet unworked, deposit of uranium- 

 ore in existence. A few years ago I found that the ashes of a 

 bituminous coal-mineral, called kolm, which is abundantly asso- 

 ciated with the Cambrian alum- slate of Vestrogothia and Nerike, 

 contain nearly 3 per cent, of uranium-oxide. Cleveite is closely 

 allied to the Bohemian or Cornish uranpecherz, but differs from 

 the last-named by its considerable percentage of thoria — and it is 

 especially noteworthy that this percentage of thoria seems invari- 

 ably to concur with a tolerably large percentage of nitrogen (first 

 discovered in this mineral by Hillebrand), and of helium (first 

 separated from cleveite in 1895 by Ramsay). 



The statement that uranpecherz was the first mineral in 

 which nitrogen was shown to be present, is, however, not quite 

 accurate. As far back as 1805 Valentine Rose showed that apo- 

 phyllite, a finely crystalline hydrous fluosilicate, yielded ammonia 

 when heated, and consequently contained nitrogen. Later on, 

 Berzelius showed that a great many hydrous silicates, when heated 

 before the blowpipe, yielded water containing ammonia ; and for 

 thorite he directly stated the percentage of the gases which the 

 mineral yields when heated, after the absorption of the vaporized 

 water and of free carbon-dioxide. Moreover, in 1827 Jean-Baptiste 

 CJhevallier found that natural ferric oxide mostly contained ammonia, 



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