63 

 6. Datolite (Basic orthosilicate of calcium and boron). 



Mr. R. Williams, mine manager of the Colebrook mine- 

 North-East Dundas, has kindly forwarded me some fine 

 s]3ecimens of this recent addition to the already long list of 

 minerals known to occur in this island. They were obtained 

 at that mine in sinking a shallow shaft in the western portion 

 of the limurite outcrop. This mineral occurs in irregular 

 crystalline masses, with a glassy lustre, and of a pale green 

 colour. Mr. E. H. Walcott writes me regarding some 

 samples which have been sent to him, that " one specimen 

 shows a rough crystal outline of what might be the ortho 

 and clinodomes, each of which is built up of a number of 

 incomplete monoclinic crystals. It gives at once a strong 

 boric acid reaction on introduction into the blowpipe flame, 

 aud fuses readily." It is supposed to be the first discovery 

 of this mineral in Australasia. 



7. Fayalite (Iron olivine). 



Abundant in microscopic crystals of a bright red colour in 

 fayalite-basalt from the Alexandra Battery, near Hobart. 



8. Idocrase (A basic silicate of calcium, aluminium, and 

 iron). 



I am indebted to Mr. W. R Bell for some extremely fine 

 specimens of this mineral, which he informs me occurs in 

 considerable masses at the Hampshire Hills. It is commonly 

 in well-developed imbedded crystals of a rich brown colour, 

 with the facets highly polished. In some rare instances the 

 crystals are fully one inch in diameter, and often show 

 peculiar modification. The massive portions sometimes con- 

 tain patches of highly coloured amethyst, with occasional 

 groups of black ilvaite, and then form very attractive speci- 

 mens for the cabinet. 



9. Ilvaite (A basic orthosilicate of iron and calcium). 



Obtained associated with idocrase from the Hampshire Hills. 

 It occurs as imbedded crystals, occasionally measuring up to 

 half-an-inch in diameter. 



10. Palagonite (Hydrous silicate of iron, etc.). 



This substance has been obtained near Perth, in the usual 

 amorphous masses of a yellowish brown colour. 



