vicinity of Dublin. 277 



5. The Andaluslte of Douce mountain is accompanied, as has 

 been mentioned, by a crystallized mineral, the characters of which 

 have much affinity to those of indurated talc ; and which is placed 

 under that denomination in the collection of Dublin College (Nos. 

 405, 6, 7) ; and a specimen of the same kind, stated to be from 

 Gkndalagh in the County of Wicklow, was found in the same col- 

 lection (No. 404.) 



The crystals are rhomboidal prisms, of which the length is in 

 some instances more than twice the breadth, but no acumination is 

 observable. They are easily cut by the knife, faintly translucent, 

 their colour yellowish-grey. Small fragments before the blowpipe 

 appear to swell a little from the separation of the folia on the first 

 application of the heat; they become white, and give with some dif- 

 ficulty a solid white enamel. The specimens to which I have access 

 at present do not enable me to give any detail of the remaining 

 characters. 



The connection of this substance with the Andalusite of Douce is 

 remarkable ; the latter often forming the nucleus of crystals exter- 

 nally of four sides, sometimes filling nearly the whole of the interior, 

 but in other specimens, forming little more than an axis, with 

 rounded edges, and of irregular form, from which the folia of the 

 investing talc-like substance appear to radiate. 



The occurrence of indurated talc in crystals has hitherto been very 

 rare : it is not mentioned by Jameson ; and Brochant, though he 

 quotes from Emmerling the rhomboidal prism as one of its forms, 

 expresses doubt as to the correctness of the statement ; I therefore 

 do not give that name to the crystals found at Douce, without some 

 uncertainty. 



6. Hollowspar^ Jameson. (Macle^ Haliy). Very distinct spe- 

 cimens of this mineral have been found by Mr. Davy at Jghavanagh 



