110 Mr. Brooke on Poonahlite, 



make the subject of a distinct communication, having satis- 

 factorily ascertained that Zeagonite, Abrazite, Aricite and 

 Phillipsite are one and the same mineral. 



Velvet Coppei- Ore of Werner. 

 On dissolving this mineral in dilute nitric acid, a skeleton 

 remains which is insoluble in any acid ; and when the very 

 minute portion I had to examine was placed on charcoal before 

 the blowpipe with a drop of nitrate of cobalt, it ultimately be- 

 came black; whence I concluded it to be silica. The part dis- 

 solved in the dilute acid contained sulphuric acid, copper and 

 zinc. 



Native Nickel, 



so called, although a sulphuret. I have measured the fibres 

 of this substance, and find them regular hexagonal prisms with 

 apparent cleavages oblique to the axis, but the cleavage planes 

 are too imperfect for accurate measurement. 

 Poonahlite. 



I am indebted to the kindness of Mr. Heuland for some 

 specimens of a beautiful variety of apophyllite from Poonah, 

 in the East Indies, accompanied by some slender crystals, 

 which I at first supposed were mesotype or needle-stone, 

 but which differ from both substances in measurement; the 

 Poonahlite being a rhombic prism of 92^ 20'. The crystals 

 traverse the mass of the apophyllite and matrix instead of 

 forming groups in the cavities ; and among several hundred 

 crystals which I have examined on my own and on Mr. Heu- 

 land's larger specimens, I have not observed one with a na- 

 tural termination. The hardness is nearly the same as that 

 of needle-stone, as far as I can discover from an experiment 

 on very small crystals. 



Glaucolite. 



This mineral has a cleavage parallel to the planes of a 

 rhombic prism of 143° 30' nearly. 



Couzeranite. 



This is described in Leonhard's Handbuch, as a right rect- 

 angular prism, and by Dufresnoy in the Ann. de Chim. et de 

 Phys. xxxviii. p. 280. as an oblique rhombic prism; and it would 

 appear from the analysis of the latter to be a distinct species 

 of mineral. Mr. Heuland has lately supplied me with a spe- 

 cimen containing this substance in small imbedded crystals ; 

 on examination of which I find that it has the form, cleavage, 

 and angular measurements of felspar. The crystals are small, 

 and the matrix in which they are imbedded is partly white 

 and partly black. Those in the white part are colourless and 



translucent; 



