"Vol. 65.] NEPHRITE AND MAGNESIAN BOCKS OF NEW ZEALAND. 371 



Chemical composition. — A number of analyses of New 



Zealand nephrite have been made by different workers, and the- 



chief of these are here tabulated for reference and comparison 

 (see Analyses I-XV, p. 370). 



The following additional analyses, made by me on a series of five 

 specimens, show the variation in percentage of ferrous oxide with 

 variation in colour : — 



XVI. XVII. XVIII. XIX. XX. 



(ieep green) (medium green) (olive-green) (pale green) (greenish white). 



Si0 2 



A1„0 3 



... 5625 

 042 



5601 

 0-65 



1-88 

 5-02 

 2065 

 13-41 

 0-45 

 0-28 

 2-03 

 029 



55-89 

 2-34 

 2-39 

 2-34 

 18-72 

 13-97 

 0-51 



221 



041 



98-78 



57-45 



1-09 



0-24 



1-35 



20-61 



15-41 



051 



2-65 



0-28 



99-59 



58-28 

 0-88 



Fe o 3 



1-67 



0*29 



FeO 



MgO 



OaO 



;N a „0 



5-61 

 ... 20-55 

 ... 12-67 



0-35 



0-35 

 22-08 

 14-98 



0-42 



K 2 



H 2 



1-89 



0-38 

 1-98 



MnO 



0-33 

 ... 99-74 



trace 



Totals 



100-67 



99-64 



It should here be pointed out that the commonest variety of' 

 New Zealand nephrite is the green kawakawa, with an iron- 

 oxide percentage varying from 4 to 6. 



As regards the minor constituents, alkalies have not generally 

 been estimated in former analyses of nephrites ; but the recent 

 extensive series of analyses by Walden [12, pp. 146 et seqq.~] have 

 demonstrated the almost universal presence of one or both of 

 the alkalies in nephrite, and such proves to be the case in the 

 specimens analysed by me. 



Chromium is not a regular constituent. Out of eight specimens 

 tested I found it in only one, and a slide cut from this specimen 

 showed grains of chromite under the microscope. Chromium-com- 

 pounds certainly do not constitute a pigment in the New Zealand 

 stone. Manganese is very generally present in small quantities, 

 as recorded also by "Walden [12, he. cit.] and by Dieseldorff [5] ; 

 while the latter found traces of copper in one specimen. It may 

 here be noted that his specimens were from a locality where copper- 

 ores have been located and prospected. 



Chemical constitution. — Dr. F. Berwerth, from his analyses, 

 of New Zealand nephrite, deduced the formula? : 



Si 20 Fe 2 Ca 5 M gll H 6 O 61 , 



Si 20 Fe 2 Ca 5 Mg u H s O6i, 



and Si 20 FeCa 5 Mg i2 H 6 O 61 , 



