80 Mr HAIDINGER on the Parasitic Formation 



only extensive collections, or the large quantity gathered and 

 preserved on the spot, both of 4 which I had the good fortune to ' 

 examine, will allow of observing perfect and continuous passages 

 from one extreme to the other. The series begins with such 

 crystals as not only possess the shape of the blue copper, but 

 likewise consist of that substance, with the exception of small 

 particles of the green fibrous malachite, which appear like some- 

 thing foreign, accidentally imbedded in the otherwise homoge- 

 neous mass. It terminates in such varieties as scarcely betray 

 the original shape of the hemi-prismatic crystals, the last blue 

 particles having disappeared, and the fibres grown out even be- 

 yond the original surface of them, and shewing disengaged crys- 

 talline terminations. The intermediate members distinctly pos- 

 sess the shape of crystals of the blue copper, nay, they have oc- 

 casionally even particles of the original substance here and 

 there distributed over their surface, which, to the last, preserve 

 a parallel position. These particles are not displaced by an in- 

 crease of bulk of the newly formed species. The chemical diffe- 

 rence between the two species is not considerable. Several ana- 

 lyses published by KLAPROTH, VAUQUELIN and PHILLIPS, agree 

 very nearly with the formulae proposed by BERZELIUS, which are, 

 Cu Aq* + 2 Cu C 2 , for the blue copper, and Cu C + Aq 

 for the malachite. The proportions of the ingredients are, 



Blue Copper. Malachite. 



Oxide of Copper, 69-16 71-89 



Carbonic Acid, 25-61 19-96 



Water, 5-23 8-15 



The change effected during the process of decomposition is 

 the loss of a portion of carbonic acid, which is compensated by 

 an additional quantity of water. If the formulae above men- 

 tioned are resolved into their constituent parts, as given sepa- 

 rately in the analysis, the blue copper is composed of three 



