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Physical and optical pro'perties. The specific gravity was 

 for the crystals of type III determined by the Pyknometer to 

 be 3-6122 (average of 3-5119 and 3-5125). According to 

 Moberg the crystallized steenstrupite from Kangerdkiarsuk 

 (Type I) has the specific gravity 3-40 — 3*47, while the massive 

 3-1901; Lorenzen gives З-З8 without mentioning, whether 

 crystallized or massive. The hardness of the crystals of type III 

 is a little over 5, with the other formations 4 — 5. The mineral 

 is brittle: the crystals of type III have very slight basal 

 cleavage, the fracture is conchoidal; the other formations are 

 without any trace of cleavage. The crystals of type III have 

 vitreous luster; the color is brown-black; the crystals of type I 

 and II have on the crystal faces almost metallic luster, which on 

 the first is bright black, on the last generally dull brown-black; 

 both have brownish-black shining fracture surfaces. The dia- 

 phaneity is very insignificant; when cut thin the crystals of 

 type I and II appear of a brown -yellow or brown -gray colour, 

 with the exception of the marginal zone, which in most cases 

 is blackbrown; those of type III are distinctly dichroitic; the 

 color is yellow -brown for rays, whose vibration is -^ the 

 axis с and lighter brown or gray-brown for rays, whose vibra- 

 tion is -L this axis. The streak of the crystals of type III is 

 perfectly colorless ; the other types have in the outer strata 

 of the crystals a intense brown streak, while the inner parts 

 have only a slightly colored one. There are many different 

 kinds of occlusions , fewer with the crystals of type III , which 

 are sometimes entirely without them; with the other types 

 however they appear in great numbers. Some of Ihe most 

 conspicuous of these are the very small black interpositions 

 mentioned by Moberg, which often lie in very regular rows, 

 forming a right angle with the nearest crystal face and having 

 acute limits, where the different directions meet; these inter- 

 positions are generally without any regular shape, but in most 

 cases they are more or less bushy. Further must be mentioned 



