cf the Vicinity of Dull'm. 379 



the specimens from Douce, to which I have access at pre- 

 sent ; these specimens however are not very distinct, and 

 I give this imperfect description, only with a view to point 

 out this suhstance as deserving of further examination. — 

 Its colour is yellowish grey, approaching in various de- 

 grees to yellowish white : it is translucent in about 

 the same degree as wax. 

 The form under which it has principally occurred, is that 

 of four-sided prisms, nearly square, the length of which 

 is in some instances more than thrice their breadth, 

 without any visible acumination. The surfaces of these 

 prisms are uneven, and their angles ill defined. 

 The fracture, transversely to the axis of the prisms is ir- 

 regularly curved-foliated, and splintery ; exhibiting nu- 

 merous scaly distinct concretions sometimes radiating 

 from the centre, the lustre of which is splendent and 

 pearly. In the direction of the axis, the fracture seems 

 to be uneven passing into splintery. 

 It is scratched by calcareous spar, and easily cut by the 

 knife ; with a strong pressure it leaves a whitish trace 

 on glass, which it sometimes scratches, apparently by 

 the action of some harder particles dispersed through it. 

 The specific gravity of some of the purest pieces that I 



could select was 2-888. 

 Before the blowpipe this substance appears to swell a 

 little, from the separation of its folia, on the first applica- 

 tion of the heat ; it becomes white, opake, and brittle, and 

 in small fragments gives, with some difficulty, a solid white 

 enamel. 



In the specimens from Donee-mountain, the connection 

 of the mineral now described with andalusiie, is very re- 

 markable; several of the prisms, which oti the outer part 

 consist of the talc-like matter, containing within a nucleus 

 of andalusite, that iii some instances fills nearly the whole 

 of the interior of the prism, but in others forms little more 

 than an axis, of an irregular figure and with rounded edges, 

 from which the folia of the investing matter appear to ra- 

 diate. The nature of the connection between these sub- 

 stances is still obscure ; but the occurrence of talc ia 

 genuine crystals of the figure above mentioned, has not 

 hitherto been stated on any good authority; and it is not 

 altogether improbable, that the prismatic form assumed by 

 ihe suhjiancc now under consideration, may really be that 

 of andalubite ; the latter mineral having been wholly or 

 partially removed, and the talc-hke matter moulded in its 

 place. 



B b 2 6. Hoi' 



