1835.] Analysis of Orucilite. 143 



crystals being arranged in the form of a St. Andrew's cross. 

 On measuring the angles at which these crystals crossed 

 each other, I found them to be of the value of 60° and 120°. 

 The crystals themselves were oblique four-sided prisms, the 

 acute angle measuring 59|°, but so near 60° that I have no 

 hesitation in considering the latter number as expressing 

 its true size : the obtuse angle measuring nearly 120° by the 

 common goniometer. From the cruciform disposition of 

 the crystals, it is proposed to term the mineral wucilite. 



Before the blowpipe it behaves like peroxide of iron. The 

 crystals are red externally, occasioned probably by the par- 

 tial absorption of carbonic acid, which has converted them 

 superficially into a similar combination with rust which is 

 soft and pulverulent. Internally they are black, and pos- 

 sess the metallic lustre ; streak black shining ; cleavage 

 parallel to the faces of the crystals ; fracture uneven ; pos- 

 sesses no action on the magnet ; sp. grav. 3*579, which is 

 probably below the true density, as the portion with which 

 this number was determined, was decomposed. 25 gr. of 

 the crystals reduced to powder were digested in nitric acid, 

 and a little muriatic acid was added to increase the action 

 which was slow with the former agent alone ; a small por- 

 tion of silicious looking matter remained, which was edulco- 

 rated, and its weight noted. After ignition it assumed a 

 yellowish colour, and dispersed through it minute scales 

 of mica could be distinctly detected, and its appearance was 

 precisely similar to the sandstone in which the crystals 

 were seated. It was insoluble in boiling acid, and when 

 fused with carbonate of soda, alumina and silica were sepa- 

 rated, while some micaceous scales remained undecomposed. 

 It had obviously, therefore, been mechanically attached to 

 the mineral, although care had been taken to separate the 

 crystals as entirely as possible from the native rock. 



The liquid which was separated from this insoluble resi- 

 due was precipitated by ammonia. A copious precipitation 

 of iron ensued, which, after being well washed with hot 

 water, was dissolved off the filter with dilute muriatic acid. 

 The solution was boiled with caustic soda, which threw 

 down the iron. This precipitate was again dissolved in 

 acid, and thrown down by caustic ammonia. The superna- 

 tant liquid was saturated and precipitated by carbonate of 



