E, T. Sardman — Substitution of Zinc for Magnesium. 2U3 



satisfied myself with regard to its presence, reserving the quantitative 

 determination until I shall have completed the testing of a number 

 of specimens ; but it may he worth while to mention the rocks and 

 minerals already searched. 



1. Granite. — Wicldow and Wexford range variety •} from Graigue- 

 na-spiddoge, near Carlow. — Obtained from heart of qudrry : (a) A 

 very coarse-grained light grey rock, porphyritic in parts, containing 

 white mica, together with a dark greenish magnesian variety ; also 

 tourmaline. The portion taken for analysis was prepared in such a 

 way as to contain a preponderance of mica, and four analyses of this 

 were made in the wet, as well as others in the dry, way, ere I 

 allowed myself to be perfectly satisfied as to the presence of zinc. 

 The quantity of this was very small, as was of course to be expected. 

 Traces of copper and lead were also noticed. 



(h.) Mica. — After many searches at the same quarry, I was for- 

 tunate enough to find a mass of mica sufficiently large for analysis 

 with the blowpipe. It was mostly white, but contained laminse of 

 green mica. About four grains were treated on charcoal before the 

 blowpipe, with carbonate of soda. Two metals were reduced, which 

 proved to be copper and zinc. The zinc spangles dissolved with 

 rapid evolution of hydrogen in a barely acid solution of hydrochloric 

 acid. The solution evaporated to dryness, moistened with nitrate of 

 cobalt, and heated on charcoal, gave the characteristic green re- 

 action.'^ 



2. Serpentine (?). — A green soft steatitic rock from Garrarus 

 Strand, near Tramore, Co. Waterford. This rock occurs among 

 Silurian limestones and slates, near masses and dykes of felstone, 

 etc. Some of the limestone can be distinctly seen to pass into Ser- 

 pentine. Examined qualitatively for zinc : found it present in fair 

 quantity, all the re-actions being most distinct. 



This rock contains about 8 per cent, of water, and 11 per cent, 

 of carbonic acid (COg).^ 



3. Basalt. — Already described. 



4. Black Mica. — In a gneissose or granitic rock. Locality un- 

 known. Specimen from Geological Survey collection.* The mica 

 is perfectly black, and occurs in quantity in small flakes thickly 

 massed together. 



About four grains were treated at a time before the blowpipe 

 with carbonate of soda. After fusion the mass yielded a notable 

 quantity of copper, a very appreciable amount of zinc, and a trace 

 of a metal which seemed to be lead. All the characteristic tests for 

 zinc were answered very distinctly. 



5. CJilorite schist (? Talc schist). — With inclosed grains of glau- 

 conite (?). From Geological Survey Collection. The examination 

 with the blowpipe gave two metals, both in very appreciable 



1 Leinster Granite. 



* The zinfc most probalily occurs here in the dark magnesian mica. 

 ^ It is therefore not entirely metamorphosed. 



* The specimens from the Survey Collection were obtained by the kind pefmissioii 

 of Prof. Hull, F.R.S., Director of the Geological Survey of Ireland. 



