Z22 [Proc. B.N.F.C, 



Since the first announcement of hullite as " a hitherto 

 undescribed mineral "* from Carnmoney Hill, Co. Antrim, the 

 substance thus described has been subjected to examination in 

 various quarters. But I venture to think that, familiar as this 

 material is to geologists in the North of Ireland, there is still 

 something to be said concerning its true nature. 



E. T. Hardman f describes the "mineral" as "filling 

 amygdaloidal cavities"; Prof. Hull,! on the other hand, in his 

 notes, speaks of it as " large and small grains of an opaque, black, 

 dense mineral, with smooth, somewhat conchoidal, fracture, and 

 brown streak," forming part of the "paste" of the basalt. Both 

 these statements are, however, correct, since " hullite " occurs 

 interstitially among the minerals of the rock, as well as in mam- 

 millated and minutely stalactitic forms coating the numerous 

 steam-vesicles. I have not been able to verify Prof. Hull's 

 remarks as to the abundant occurrence of olivine in the Carn- 

 money rock, which, from my own sections, I should regard as 

 being on the verge of the pyroxene-andesites and aphanites, 

 rather than as an olivine-basalt. M. Lacroix records olivine, 

 however, and the mass is clearly variable in mineral composition. 



I fail to understand E. T. Hardman's remark that microscopic 

 sections show that " the mineral is perfectly distinct from, and 

 does not merge into any part of, the basalt." Prof. Hull appears 

 very properly to contradict this by his own statement some nine 

 lines lower down; and E. T. Hardman himself observed how the 

 " hullite " was deposited in spaces between the augite and other 

 crystals. Surely in such cases it formed an integral part of the 

 basalt. 



His careful analysis is of historic interest, as one of the first 

 cases in which Sonstadt's method of sepaiation, by the use of a 



* E. T. Hardman, " On Hullite, a hitherto undescribed mineral ; a Hydrous 

 Silicate of peculiar composition, from Carnmoney Hill, Co. Antrim, with Analysis. 

 With Notes on the Microscopical Appearances, by Prof. Hull, F.R.S." Proc. Royal 

 Irish Acad., ser. II, vol. Ill (1878), p. 161. 



t Ibid, p. 164. 

 % Ibid, p. 1 66, 



