Analyfis of the Spinel Ruby. 4£ 



the tides and currents ; and others, a change in the earth's 

 centre of gravity, occaiioned either by depofits tranfported 

 by rivers to the fea, or by the progreffive movement of fome 

 mafs detached from the interior parts of the earth fuppofed 

 to be concave *, 



[To be continued.] 



VII. Analyfis of the Spinel Ruby. By C. VAU&UELIN, 

 Infpetlor of Mines and Member of the French National In- 

 flitute. From Journal des Mines, No. XXXVIII. 



I 



RON and manganefe have long been confidercd as almoft 

 the jnly metals employed by nature to colour minerals ; 

 but though thefe metals may aflume a multitude of different 

 fhades according to the proportions of oxygen which they 

 contain, we however often fee in nature bodies poffefled of 

 colours which neither iron nor manganefe ever formed arti- 

 ficially or naturally when pure, and it is probable that we 

 (hall one day find many other colouring metals and alfo 

 ftones and earths. 



I have already announced that the colour of the emerald, 

 which all chemifts afcribed to iron, is owing to the oxyd of 

 chrome. In examining the peculiar red colour of the fpinel 

 ruby with the refults of the analyfis lately made of it by 

 ProfefTor Klaproth, I began to doubt of that rich and beau- 

 tiful colour being produced by the oxyd of iron, of which 

 the ProfefTor found only 1*5 in 100 f. My doubts in this 

 refpe6t were fiill increafed by reading in Bergmann that the 

 ruby fufed with borax communicates to it a beautiful green 



* 12. To obforve whether there are not daily formed different kinds of 

 Hones in the places which are wafhed by the waters of the fea. C. 



t The number, nature and proportion of the principles found by Klap- 

 roth in the fpinel ruby are ftated as follows: Alumine 76 ; filiceous earth 



j6; mngnefia 8$ oxyd of iron 1*5: — Total 101-5. 



colour, 



