186 



PROCEEDINGS OF THE ACADEMY OF 



[1889. 



apple and emerald-green. The material fur the analysis was picked 

 with the utmost care, especially to exclude the minutest crystals of 

 chloanthite. The quantity analyzed was 0*2805 gram. In closed 

 tube it yields water and turns brown. It is infusible even in the 

 Bunsen blowpipe, but the green color returns at this high tempera- 

 ture, and the specimen looks as if it had not changed. It gives 

 with the fluxes only nickel reaction. It is easily decomposed by 

 hydrochloric acid, a little less after ignition, and separates flocculeut 

 silica. Owing to the scantiness of material, the substance was first 

 ignited then digested with concentr. hydrochloric acid over night. 

 The silica was then fused with sodic carbonate, when it was observed 

 that it had lost 10%, showing that 90% of the ignited silicate had 

 been decomposed by the acid. The analvsis gave: — 

 Si O 2 = 31-62 



9-44 at 100° C. 



97-71 ( 7-14 at 600° C. 

 The arsenic oxide is undoubtedly contained as such in the min- 

 eral. Let it be assumed then that it is admixed in the form of 

 there will be : 



Coeffic : 



Annabergite, 



SiO 2 



MO 



TnO 



FeO 



CaO 



MgO 



H 2 



As 2 5 



NiO 



H 2 O 



31-02 

 33-62 

 4-00 

 2-03 

 0-71 

 0-42 

 13-58 

 4-77 

 4-60 

 3-00 



0-5017 

 0-4508 ^ 

 0-0490 

 0-0290 

 0-0120 



0-7500 



V 



0-5408 



Annabergite. 



H 2 



0-75 

 1-5 



For the silicate the ratio will be 



(Ni, Zn, Fe) O : Si O 2 

 0-5408 : 0-5017 



1-08 : 1 



This is the ratio exactly, given by Groth for Garnierite. (Tabell. 

 Uebersicht, 2 Aufl.) The question remains, however, is Garnierite 

 an Ortho-or a Metasilicate ? Groth takes the latter alterna- 

 tive, writing the formula 



H 2 (Ni, Mg,) Si O 4 . } aq. 

 To the speaker this view does not seem confirmed by the present 

 results. The water is expelled too readily, over one-half at 100° C. r 

 and he would write the formula 



(Ni, Tu, Fe) Si s . U aq. 

 as a metasilicate. 



