Clifton College Scientific Society, 89 



bright bluish greea colour. It is opaque in appearance. Its specific 

 gravity is 27, and its composition is thus shown, (A!, Cr, Fe,) 812 + 6 ft, 

 i^Hausmann and Nicot). It ocurs nearly pure in small fissures in 

 the chrome ironstone, and is infusible by itself, but, on subjection to 

 the blow-pipe flame, becomes paler. 'W'ith borax, it forms an emerald 

 green globule. 



This interesting substance, though purer, does not probably much 

 dififer in composition from the chrome ochre of Silesia, which is thus 

 analysed by Zellner, — 



99.75 



This mineral is sparingly scattered around the Free Church and 

 in the neighbourhood of Ualta, and does not occur elsewhere in the 

 island. 



Asbestos is found abundantly on the serpentine of Swina Ness and 

 Keen Hill, and on the diallage to the south of Balta. Also on Balta 

 Island. This hornblendic substance, a variety of actinolite and 

 amianthus, is used for lampwicks and for making fireproof safes, 

 owing to its long, fibrous, flexible, and incombustible texture. It 

 can be woven into fire-proof cloth. It is white in colour. 



Amianthus. The locality for this is on the eastern side of Balta 

 Island, and all over Keen Hill. It is a pure variety of asbestos, but 

 much heavier, compacter, and not so flexible as the latter mineral. 

 It is of a fine, briglit gi-eeu colour, shiny, and its fibres are not easily 

 separated, as they ai'e very brittle. 



Noble Serpenline is of course found in the serpentine district round 

 Balta. The best spots for it are near Keen Hiil and Swina Xess, and 

 on the shores of the Sound. It is said to be found also in the islet 

 of Naaf Gruna. 



The Oarnels I have already mentioned as being profusely scattered 

 through the micaceous gneiss of Woodwick. 



At this place I also obtained specimens of rose quartz which had 

 garnets embedded in it. 



Along the west coast, in the ' voes,' there occurs in the quartz veins 

 of the gneiss an emerald green substance, which I believe to be 

 chrjisocolla. 



Balta Island is interesting to the mineralogist, as it contains 

 besides the aforesaid minerals, green veins of copper ore with 

 cliromate of copper in small quantities, which latter is of a bright green 

 hue, and powdery. Traces of Brucite have been observed at the 

 northern extremity of this island. 



Fine specimens of hyperstkene are found on Keen Hill and south 

 of Balta. One variety has a grey, metallic lustre, and considerable 



