62 THE MINERALS OF TASMANIA. 



but is not rarely also produced by the alteration of other 

 minerals. Occurs in the Mt. Lyell schists. (J. W. Greg- 

 ory, " The Mount Lyell Mining Field," Aus. In. Mining 

 Eng., Melbourne, 1905.) 



100. Danburite (Silicate of Calcium and Boron). 



This uncommon mineral crystallises in the orthorhombic 

 system, and is always pale in colour, of some shade of 

 yellow to almost colourless. It occurs sparingly with the 

 next species in the limurite of the Colebrook, Dundas. 



101. Datolite (Basic Orthosilicate of Boron and Calcium). 



This species crystallises in the monoclinic system. 

 Occurs in glassy crystals and crystalline aggregates ; has a 

 vitreous lustre, and is always of pale colour, usually a 

 shade of the palest green. It is of secondary origin, possibly 

 formed after axinite and calcite, with which it is closely 

 associated at its only locality in this island, viz., the Cole- 

 brook Mine, North-East Dundas. 



Writing of this Dr. C. Anderson states ('' Records of the 

 Australian Museum," Vol. VI., Part 3): — "The mineral 

 was first obtained in sinking a shallow shaft in the western 

 portion of the limurite outcrop. It is found associated 

 with axinite, calcite, and other minerals as already 

 described under axinite, and sometimes occurs in large 

 brilliant crystals. It is colourless, greenish, or yellowish. 

 Crystallography. — The crystals have mutually interfered 

 during growth, but one small projecting crystal was found 

 and measured. . . . The habit of the figured crystal 

 seems characteristic so far as can be judged by inspection 

 of others ; it is prismatic by extension parallel to the a 

 axis, and measures about 6 mm. in length. It is fairly rich 

 in forms, but, as is usual with datolite, many of the faces 

 are wavy, and give but poor reflections. The three faces 

 h (212), TT (231), and x (102) are dull, and were measured 

 in the position of maximum illumination." 



The result of Dr. Anderson's analysis was as follows,. 

 viz. : — 



99-40 



