138 



The mineral has been found in but small quantity and only 

 in the crystalline state. The crystals seldom attain more than 

 5""° in length and I — 2""" in breadth and thickness; the majo- 

 rity are considerably smaller in size. They belong to the mono- 

 clinic system and are fairly regularly developed, so that fairly 

 accurate measurements could be obtained. The crystallographical 

 constants are derived from the following angular values: 



(130): (130) = 120° 15', (l30):(00l) = 88° 19', and 



(101): (001) = 53° 21'. 

 The axial ratios calculated from them are 

 a\b:c = 0,5813 : 1 : 0,8501. 

 ß = 93° 23'. 



According to these constants the forms present have the 

 following symbols: 



a = {lOO}, Ô = {OIO}, с = {OOl}, a. = {01l}, d = [ю\] , 



'm = {ll0}, w = {l30}, s = {112}, p = {u\], 



д = {ш}, r = {263}. 



Nearly all the crystals of this mineral that I have observed 

 are very like one another with regard to their habit. Only as 

 regards the presence or absence of certain subordinate forms 

 do they present any variation. The forms that are always pre- 

 sent and give the crystals their constant habit, are c, b and ?/. 

 The crystals are always elongated in the direction of the a-axis 

 into rectangular prisms, bounded in the longitudinal zone by 

 the second and third pinacoids. The crystals are always ter- 

 minated by the form w, the faces of which form the wedge- 

 like ends that characterize the leucosphenite crystals (Fig. 4, 

 Plate VII). The faces of the third pinacoid are generally pre- 

 dominant, so that the crystals are more or less tabular parallel 

 to them. However there occur individuals on which the said 

 pinacoids are almost equally developed (Fig. 9, Plate VII) or 



