ORDER Viii. PRISMATIC TITANIUM-ORE. 375 



Colour brown, yellow, grey, green ; they are 

 not lively, some pistachio-green ones excepted. 

 Streak white. Transparent ... translucent on 

 the edges. 



Hardness = 5-0 ... 5-5. Sp. Gr. = 3468, of a 

 massive yellowish-grey variety from Norway. 



Compound Varieties. Twin-crystals : faces of 

 composition parallel, axis of revolution perpendicu- 



"pj 



Jar to ; sometimes the individuals are conti- 

 nued beyond the face of composition. Massive : 

 composition granular or lamellar ; the first are very 

 strongly connected. 



OBSERVATIONS. 



1. The preceding regular forms are given entirely on the 

 authority of Mr G. ROSE. Most of the forms depend upon 

 the parallelism and situation of some of their edges of com- 

 bination, yet some doubt still remains in regard to the best 

 position to be chosen for the crystals of the species, which 

 may be probably brought to a still higher degree of simplicity. 

 The two species of the Wernerian system, the Brown and the 

 Yellow Menachlne-ore^ or Titanite and Sphene^ differ chiefly 

 in their colours, and the degrees of transparency connected 

 with them. The first is brown, and almost entirely opake, 

 while the last is of various pale brown, yellow, green, and 

 grey colours, and at least translucent. These two species, 

 like Hyacinth and Zircon, or Beryl and Emerald, are frag- 

 ments of the intimately connected series of varieties which 

 together form the natural-historical species of prismatic 

 Titanium-ore. 



2. The varieties of the present species consist of 

 Lime 33-00 32-20. 

 Oxide of Titanium 33-00 33-30. 

 Silica 35-00 28-00. 



Oxide of Manganese a trace. KLAPROTH. 0-00. CORDIER. 



