On the Dichroism of two European Andalusites. 529 



No. 3. Derbyshire . . No gallium. 



No. 4. Cornwall (?) . Eich enough. 



No. 5. Weardale . . Eich in gallium. Seems to be a 



little richer than the preceding. 

 No. 6. Fowey Consols. Eich. Seems to be somewhat 



richer still than the preceding. 



M. Lecoq de Boisbaudran adds that some of the English 

 blendes thus appear to him to be at least as rich in gallium as 

 the Bensberg blende is, and that, judging from the intensity 

 of the gallium-lines shown, he is inclined to think the Fowey- 

 Consols blende is even superior to that from Bensberg. 



I should add that the Fowey-Consols blende here spoken 

 of is the well-known mamillated nodular material of that 

 locality. 



Should any member of the Society wish to see a portion of 

 the original specimen, or to examine with the spectroscope 

 sections thereof or of the Oxford mineral, I am. prepared to 

 submit them to him. 



LXV. On the Dichroism of two European Andalusites. 

 By W. Gr. Lettsom, Esq.* 



TWO years ago or so there was received in London from 

 Brazil a batch of Andalusites, the transparency of which 

 allowed of their remarkable dichroism being well observed. 

 This induced me to make trial as to the amount of dichroism 

 which Andalusites from European localities might exhibit if 

 suitably cut by a lapidary: for none of our Andalusites that I 

 am acquainted with are capable of being examined, as is the 

 case with Brazilian specimens, in their natural state. 



I beg leave to lay before the Society a few sections of Anda- 

 lusite from a locality in Germany the name of which I have 

 not at hand, but which I hope to obtain in a day or two. 

 Those sections show in one image a rich chocolate-brown 

 colour, the other being all but colourless. 



Other sections, from Goldenstein in Moravia, exhibit, in one 

 image a deep blood-red colour, the other image in this case 

 too being almost colourless. 



* Communicated by the Crystallological Society, having been read 

 November 23, 1878. 



