C. H. Palmer — Remarkable Case of Hydration. 45 



Aet. IY. — Chrysocolla: A Remarhable Case of Hydration; 

 by Charles M. Palmer. 



Somewhat over a year ago a cjuaDtity of medium grade 

 oxidized copper ore from Pinal Connty, Arizona, came into the 

 writer's hands, with the information that it was representative 

 of the class of ore that was being shipped to the smelters, and 

 that as the latter were claiming the presence of surprisingly 

 large quantities of moisture, sometimes as high as 16 or 17 per 

 cent, it seemed to be a matter for investigation. The ore con- 

 sisted mostly of bluish or greenish chrysocolla impregnating 

 or filling seams in a siliceous matrix, and occasionally as an 

 incrustation ; sometimes, however, being associated with a black 

 variety containing considerable manganese. 



Water determinations were made on several lots which gave 

 results varying from about IT to 20 per cent, which, for an air- 

 dried ore carrying but 12 or 14 per cent of copper, was some- 

 what unexpected and remarkable. Then several large pieces 

 of enamel-like turquoise blue chrysocolla were picked out, which 

 seemed to be comparatively pure, and these were powdered pre- 

 paratory to analysis (sample No. 1 ) with the view of getting 

 more light on the character of the mineral. One gram was 

 weighed out on a watch glass one evening and placed in a dessi- 

 cator over concentrated sulphuric acid. The next day upon 

 weighing for determining the loss under these conditions and 

 finding it, according to my weights, to be over 12 per cent, I 

 thought I had simply made one of those unaccountable mis- 

 takes in my weights that will sometimes happen, and there- 

 fore promptly weighed out another portion, which gave prac- 

 tically the same result. The material gave the following upon 

 analysis : 



Silica (insoluble) _ . 38'64^ 



Cupric oxide _ 25-22 



Alumina _ . 11-76 



Ferric oxide trace 



Water (over H^SOJ 12-36 



Water (additional loss at red heat) 12-22 



100-20 



An effort was made to obtain a purer specimen, and from a 

 lot of ore from another locality in Arizona, another sample 

 (sample No. 2) of deep blue chrysocolla, apparently pure and 

 perfectly homogenous in appearance, was carefully picked out. 

 It lost 18-24 per cent after 22 hours in a dessicator over sulphuric 

 acid, which loss was increased only to 18*96 per cent after 33 days 



