PHYSIOGRAPHY. 297 



Kyanite. 



with P. Fracture uneven. Surface streaked parallel to 

 the common edges of intersection. 



Lustre pearly upon M, particularly if the face is produced 

 by cleavage ; inclining to vitreous upon the other faces. Color 

 generally white, often passing into blue, sometimes inclining 

 to green or grey, and rarely to black. Frequently spots of 

 berlin-blue elongated in one direction, upon a paler ground. 



Streak white. Transparent . . . translucent. 



Brittle. Hardness = 5-0 ... 7-0 ; the lowest degrees 

 upon M, the highest on the solid angles and edges. Sp. gr. 

 = 3'675, a blue, transparent variety cut and polished ; 

 3'559, a milk white variety of Rhaetezite. 



Compound Varieties. Twin-crystals : faces of compo- 

 sition parallel, axis of revolution perpendicular to M. Mas- 

 sive : composition broad columnar, sometimes straight la- 

 mellar, often curved, or divergent ; faces of composition in 

 most cases irregularly streaked. 



1. Two varieties were formerly distinguished as particular species, 

 Kyanite and Rhatizite : the former referring simply to such varieties 

 as are blue, the latter to those whose color is white. The Fibrolite of 

 Count BOURNOIV must also coalesce with the present species, with which 

 it perfectly agrees in every property. 



2. Before the blow-pipe, Kyanite is infusible. With borax, it is solu- 

 ble with great difficulty. Some crystals exhibit positive, others nega- 

 tive electricity, on being rubbed. 



3. Analysis. 



BySAUSSURE. By.LAUGIER, ByKLAPKOTH. ByCHENEVIX- 



var. Fibrolite. 



Alumina . 54-50 . 55-50 . 55-50 . 58-25 



Silica . 3062 . 3850 . 43-00 . 3800 



Lime . 202 , 0-50 . 000 . 0-00 



Magnesia . 2-30 . 0-00 . 0-00 . 0-00 



Oxide of iron 6-00 . 2-75 . 050 . 0-75 



Water . 4-56 . 0-75 . 0-00 . 0-00 



Potash , 0-QO . 0-00 . a trace . 0-00 



