ON ARSENIATED COPPER. 1 $9 



The lamince divide parallel to the large faces with great 

 eafe. Their colour is a fine grafs-green. 



3. Acute odlahedral arfeniated copper, CPig-^): Incidence 

 of r on /, 96°, according to M. de Bournon ; of / on l^, 1.12^, 

 The colour is a brown green more or lefs deep. 



a, cuneiform. The preceding oflahasdron lengthened fo 

 that the terminal edge is parallel to n. This form, which is 

 the mod common, oiFers the appearance of a long rhomboidal 

 prifm, more or lefs acute, and is terminated by dihedral fum- 

 mits. 



4. Trihedral arfeniated copper. In a ftrait triangular prifm, 

 which is at the fame time equilateral, according to M. de 

 Bournon. 



When the cryftals have not been long expofed, their colour 

 is a fine bluifh green ; but their furface is fubje6t to change 

 and take a blackith tinge. If they are fcratched, their primi- 

 tive colour will re-appear. 



5. Capillary arfeniated copper. This Is properly the oli- 

 venerz of the German mineralogifts. 



6. Mammellated arfeniated copper. In mammellated maffes, 

 llrlated in the interior. Thefe two laft varieties are fufceptible 

 of a great diveriity of tints, which fliew the tranfitions from 

 grafs-green to olive-green, to greenifli-brown, to tawny (mor- 

 dore), to yellow, to bluifh, and to white, which is frequently 

 fat tiny. 



The following is the manner in which M. de Bournon clafled M. deBoumon's 

 the different modifications which have been jiifl mentioned, *^'^^^^"'^°"* 

 according to the differences which they offer with refpecSt to 

 form, fpecific gravity, and hardnefs. 



He divides tiiem, as I have faid, into four diflini^ fpecies. Four diftinft 

 The firfl is derived from the obtufe o6tahedron : the type of ^P"'^^* 

 the fecond is the lamelliform cryflal, in hexagonal laminse, 

 with bevils inclined alternately in contrary diredions. He 

 takes the acute odahedron for the primitive form of the thirds 

 and conne£ts the acicular cryflals and mammelary concretions 

 with it, as varieties : in the fourth he places the equilateral 

 triangular prifm, and feveral other forms which offer the fame 

 prifm, truncated on its folid angles or on its edges. 



On the other hand, Mr. Chenevix has given fix refults of Mr. Chenevlx's 

 the analylis of arfeniated copper, which I fhall detail, difpofing^^^'j'*^^* 

 them conformably to the order efiablidied by M. de Bournon. 



Firft 



