Vol. 56.] OF MINERALS CONTAINING RARE ELEMENTS. 523 



felspar-quarry at Ytterby was likewise the only locality for gadolinite 

 and yttrotantalite until 1814, when these minerals were discovered 

 by JBerzelius and Gahn in the pegmatite-veins of the neighbourhood 

 of Ealun. Some thirty years later gadolinite was also met with by 

 Keilhau in an analogous formation at Hittero in Norway. Since 

 then several new localities for gadolinite have been discovered in 

 Sweden and Norway, as well as in North America. Moreover, 

 several other minerals have been found, containing gadolinite-earths 

 as essential ingredients : all of them are, however, of rare occur- 

 rence. Most of them are found only in pegmatite-veins in Scandi- 

 navia, chiefly within a broad, geographically well-defined zone 

 extending on both sides of the 60th parallel of latitude, from the 

 northern shore of Lake Ladoga across Southern Finland, Central 

 Sweden, Southern Norway, and as* far as the south-western coast 

 of Greenland. In the course of the last few years some localities 

 closely resembling those of Scandinavia have been recorded in the 

 United States. Sometimes also minerals containing yttria have 

 been found, with monazite, in considerable quantities in river-sands. 

 Outside of Scandinavia, however, these minerals are of extremely 

 rare occurrence in situ. To procure the raw material necessary for 

 obtaining only a few grammes of yttria from the mines or quarries 

 on the continent of Europe or in Great Britain would be an all but 

 impossible task. 



Among the minerals containing gadolinite-earths in any quantity 

 worth mentioning, it may suffice here to add the following : phosphate 

 of yttria or xenotime and yttrocerite, discovered by Berzelius ; 

 euxenite discovered by Th. Scheerer ; yttrotantalite and 

 fergusonite, discovered by Ekeberg and Giesecke. A detailed 

 account of these discoveries and of their great importance for science 

 cannot, however, be given here. I shall only, as an instance of the 

 interest which may attach to even apparently inconsiderable finds 

 in this respect, mention two finds of yttria-minerals made of late 

 years. 



One of the latest discovered and perhaps one of the richest 

 localities for such minerals is a pegmatite-vein at Osterby in Dale- 

 carlia. Fluocerite, otherwise very rare, occurs here rather abundantly, 

 together with a compact or indistinctly crystalline mixture of 

 orthite, gadolinite, and other minerals long known as containing rare 

 earths. Recently Herr Charles Benedicks, when examining several 

 specimens of fluocerite from Osterby, found another new yttrium- 

 silicate, differing from gadolinite in its light-yellow colour, its 

 crystalline structure, and its chemical composition. It occurs very 

 sparingly and would be little deserving of attention, did it not con- 

 tain, besides the usual constituents of yttrium-silicates, 1*5 per cent, 

 of nitrogen and helium. This comparatively large percentage of 

 inert gases which the Osterby mineral has in common with many, 

 perhaps most of the minerals containing rare earths, invests it with an 

 importance greater than it could claim on account of its composition 

 or mode of occurrence. The presence of helium has been ascertained 



