131 



trical relations with the plane of symmetry coinciding with the 

 twin-plane. 



The nature of the faces have partly been mentioned in the 

 preceding: in most of the crystals they are generally dull; a 

 few small crystals with rather bright faces may however be 

 found, especially among those from Naujakasik. Almost all 

 the faces are moreover rather uneven what is seen especially 

 distinctly on è{010) which is often of considerable size; it is 

 slightly undulating without any distinctly predominant direction, 

 which latter fact holds good also with regard to most of the 

 other faces. Combination-striation is only found in the zone- 

 portion (f, r, n) = ({OOI}, {Г02}, {Г01}), and in one single 

 case between a{lOO} and an adjacent prismatic face (/г{б10} 

 by Winther). 



Physical properties. 



The cleavage is exceedingly strong after a{lOOJ and c(oOl) 

 there is no perceptible difference between the two directions, 

 and not the sligthest trace of any third direction can be found. 

 The surface of fracture is uneven; the mineral is brittle, far 

 from being so coherent as the pectolite is sometimes. The 

 hardness is 5 — 5V2 ; the specific gravity has by Winther 

 been measured in the pycnometer to 3"089 for the mineral from 

 Tu top Agdlerkofia, and to 3'084 for the mineral from Nau- 

 jakasik. By determination with the fluid of Thoulet I have 

 found respectively 3"133 and 3'101 for these varieties, further 

 2"993 for the small crystals from Kangerdluarsuk and 2"971 

 for the mineral from Siorarsuit. The values are all greater 

 than in woUastonite and pectolite, but considerably smaller than 

 in rhodonite. 



The colour is rather varying; the mineral from Tu top 

 Agdlerkofia is in its fresh state finely rose-red, but becomes 

 brownish by transformation. The crystals from Kangerdluar- 



9' 



