120 Chronicles of Science. [Jan. 



Giving a composition 3 R S -f- 3 H, where R is equal to (Cu Ca Fe), 

 or a hyclrated subsulphate of copper, of a more basic character than 

 either langite or brochantite, having a portion of the protoxide of copper 

 replaced by lime. That the lime is actually in combination is proved 

 by the fact tbat no intermixture of gypsum could be detected by a 

 polarizing microscope.* 



Evansite is a new mineral species, which has been described bv 

 Dr. Forbes, F.R.S. 



This mineral was brought from Hungary in the year 1855, by the 

 late Mr. Brook Evans, of Birmingham, and was then reported to be 

 found in some abundance, as an incrustation, in drusic cavities which 

 occurred in the brown iron ores. It was regarded as pertaining to 

 tin mineral species allophane, with which it agrees in many of its 

 physical properties, as hardness, colour, specific gravity, &c, as well 

 as in percentage of loss sustained upon heating the mineral to 

 redness. 



The specimen received from Mr. Evans was labelled " Allophane, 

 from Zsetcznik, Gomar Comitat," and was very beautiful in appear- 

 ance, consisting of an agglomeration of small stalactites, with reni- 

 form and globular excrescences on brown hematite, many of these 

 excrescences much resembling artificial or natural pearls, hav4ng both 

 the figure and characteristic pearly lustre of each. 



The identity of the mineral with allophane being doubted, a pre- 

 liminary blow-pipe examination immediately confirmed this opinion 

 by proving the absence of silica in any quantity, and indicating the 

 presence of phosphoric acid ; consequently, Dr. Forbes was more 

 disposed to regard it as hydrargyllite or Gibbsite. 



The physical characters of Evansite are as follows : — Amorphous, 

 and without trace of crystallization ; reniform or botryoidal, colour- 

 less or milk-white, and sometimes faintly tinged with yellow or 

 blue, and occasionally presenting iridescent hues ; streak white, trans- 

 lucent to semi-opaque. Lustre, vitreous or resinous ; splendid and 

 waxy internally ; very brittle. Fracture, semi-conchoidal and 

 shining. 



Hardness 3 -5 to 4 ; specific gravity 1*939. Analysis : — 



Water 39 95 



Phosphoric acid 19-05 



Alumina 39-31 



Insoluble (silica) 1-41 



Loss 28 



100-00 



From which the following formula may be safely deduced : — 3 Al* O 3 , 

 9 PO 5 + 18 HO.f 



There is a remote — and but a remote — connection between the 

 subject we chronicle and the process of artificial petrifaction an- 

 nounced as discovered by Professor Efisio Marini, of Sardinia. It 

 will be remembered by many, that a Venetian gentleman exhibited 



* ' L's Mondes,' Nov.. 1S64. + 'Phil. Ma-.' Nov.. 1854. 



