1826.] M. Berzelius*s Annlym of some Minerals^ 117 



bule, phosphate of iron is formed in abundance. The acids, 

 even when concentrated, do not dissolve it. 

 The analysis of phosphate of yttria gave : 



Yttria 62-58 



Phosphoric acid, with a httle fluoric acid . . 33*49 

 Subphosphate of iron 3*93 



100-00 



The formula of the composition of this mineral is therefore 



analogous to that of phosphate of lime, Y^ P". As, hitherto, 

 no other native combination of yttria with phosphoric acid has 

 been discovered, it seems superfluous to give this any other 

 denomination than that of phosphate of yttria. 



Polyfnignite, 



A black, brilliant, mineral, crystallized in small prisms, is 

 sometimes found in the zircon-sienite of Fredrikswarns, whose 

 very complicated composition has induced M. Berzelius to call 

 it polymignite, {ttoKv^ et fjnywu.) 



It is black, and absolutely opaque, even on the edge; the 

 matrix, nearest in contact with it, is usually of a red colour, as 

 occurs at Finbo, with albite, if it contain yttrotantalite. 



This mineral is always more or less regularly crystallized in 

 long thin prisms, with a rectangular base, whose edges are 

 usually replaced by one or more planes ; sometimes two of the 

 planes of the prism are broader than the rest ; its length is from 

 one to four lines. Berzelius never had an opportunity of seeing 

 the extremities of the prism sufficiently developed, to enable 

 him to determine the form with any precision. 



The specific gravity of polymignite = 4-806. It scratches 

 glass, and cannot be scratched by steel. Its fracture is con- 

 choidal, without any indication of cleavage. The surface of the 

 crystals has a bright, almost metaUic lustre, to which that of the 

 fracture also approaches, and far exceeds what is commonly ob- 

 served in minerals. Its powder is brown, the colour becoming 

 clearer by trituration. 



It undergoes no change before the blowpipe, neither fusing", 

 nor losing its lustre ; it gives off" no water. With borax it fuses 

 easily, and gives a glass, coloured by iron ; if more borax be 

 added, the glass becomes opaque by flaming, and acquires an 

 orange colour ; with a still larger quantity it becomes opaque on 

 cooling. If the mineral be fused with tin, the colour becomes 

 red, inchning to yellow. It dissolves also in salt of phosphorus, 

 but with less facility ; in the reducing flame the glass assumes a 

 reddish colour, which is not altered by the addition of tin ; in 

 the oxidating flame the reddish colour becomes clearer, and in- 



