NliW MINERAL. 135 



«UogcvIier new to those most acquainted with the lauitrai pro- 

 ductions of Coimvall. 



Its colour both externally and internally varied tVoni n light External cha- 

 ash to a dark brown ; fracture like that of flint, presenting 

 sections of concentric layers ; texture close and polished like 

 that of a nut, and of a &ilky lustre ; hardness about 8 of Kir- 

 wan ; not easily broken in the mass, but its small fragments 

 very brittle: when trit\irated giving out a strong hepatic 

 odour; sp. gr, varying from 3.7 to 3.9. 



Soluble in nitric and muriatic acids vvith effervescence, vio- Solulable in a- 

 lenily decomposing the former, and giving out sulphuretcd hy- tai ^ ° 

 drogcn gas in abundance with tiie latter ; in botii instances 

 depositing a considerable proportion of sulphur. 



Precipitable from the above acid solutions by aqua kali in Precipitable by 

 a soft gelatinous form of a light cream colour, but becoming of ' 

 a pale olive green at 300'^ Fahr. ; sp. gr. of this precipitate abput 

 4.5 : the same change of colour took place at the same heat in 

 some earthy calamine from Derbyshire, of the sp. gr, 3. 

 ^764. 



Precipitable entirely from the acid solutions by prussiate of —and precipi- 

 potash ; colour of the precipitate a light i-'rench grey. a e o po as 



By the heat of an argand lamp losing about j-l^ of its weight, Its habitudes 

 owing to loss of water ; in a low red-heat 1-osing about -j\,'^ of its ^ ^^ 

 weight ; by a strong red-heat, in close vessels sublimed, in part, 

 in the form of minute acicular crystals of the silvery appear- 

 ance of similar crystals of flowers of zinc ; in the strongest heat 

 of a niQderate forge, sublimed in small prismatic crytals of a 

 brown colour, and adhering firmly to the sides of the crucible ; 

 these crystals when viewed through a microscope were in 

 colour and lustre very like brown semitransparent blende, and 

 were soluble in the nitric and muriatic acids with phenomena 

 similar to those attending the solution of blende in the same 

 acids. 



It seems worthy of remark, that a quantity not exceeding ^-^- si'^'^s fusibi- 

 .50 grains being reduced to powder and exposed to a moderate 'i^^inZ 

 forge-heat in a small crucible of platina, prepared by Dr. 

 Wollaston, enclosed in another made of earthen ware, the pla- 

 tina where in contact with the mineral was completely fused, 

 and the remaining part was covered witii an iridescent pellicle, 

 and made spft and brittle throughout its substance. 



A si mi- 



