to Defcription of the Arfeniates 



Variety 2. Capillary^ of an indeferminafe Form. 



In this variety, the very thin needle-like cryftals are not 

 terminated by the diedral apex of 112% reprefenting two 

 planes of the oAacdron, but gradually become fmaller, and 

 terminate in a very (harp pyramid. This variety has the 

 fame colours as the preceding; and its very (lender cryftals 

 are grouped in the fame manner as in that. 



Subftances in a cryftallized Hate, in pafling from a deter- 

 minate form to an indeterminate or fibrous one, frequently 

 affume an intermediate form, in which the cryftal infenlibly 

 terminates in a very acute pyramid. 



Variety 3. In Cryjiah perfeBly regular for a Part of their 

 Length, and fbrous at their Extremity, 



In this variety, the cr\'ftals are perfcft during a part of 

 their length ; but their fubftance infenfibly divides as it ap- 

 proaches the extremity, which very often is in fa(3: nothing 

 but a clufler of extremely delicate fibres, the colour of which 

 always appears lighter than that of the folid part of the cryftal. 



Variety 4. Amianthform. 



This variety is compofed of fibres as delicate as thofe of 

 amianthus, of the flexibility of which they frequently poffefs 

 a certain degree. Thefe fibres are cither parallel or divergent 

 from one common centre, in which cafe they nearly refemble 

 a hair pencil. Their colour varies confiderablv : I have feeu 

 them of different fhades of green, from a grafs green to a 

 dark brown green, of a golden brown, of a ftraw colour, of 

 a golden yellow, of a greenifh blue colour; and even per- 

 fetlly white, having frequently the luftre of fatin. 



The fibres are fometimes fo delicate, fo fliort, and fo con- 

 fufedly grouped together, that the whole appears like a dufty 

 cottonv mafsj the true nature of which is difcoverable onlv 

 by the lens. At other times, this Variety appears in fmall 

 thin laminae, rather flexible ; fometimes fcarcely perceptible 

 to the naked eye, fometimes tolerably large, and perfe£tly 

 like amianthus papyraceus. I have feen the lall-mentioned 

 form of this variety, of a light green colour, and alfo of a 

 very delicate white. 



Variety 5. Hematitiform, 

 This variety is in layers, either flat or mamillated ; and 19 

 of a fibrous texture; but is rendered conipatl by the clofe 

 manner in which the fibres are united to each other, in the 

 fame way as is obfcrved in many martial hematites, and 

 mure particularly ia that kind of tin ore which is known by 



the 



