Hardman and Huli, — A Hitherto Undescrihed Mineral. 161 



IXXVII. Olf HULLTTE, A HITHERTO UNDESCHIBED MlJfEEAL ; A HyDEOUS 



Silicate oe peculiar composition, from Caenmoney Hill, Co. 

 Antrim, with Analysis. By Edwaed T. Haedman, F.C. S., H.M. 

 Geological Survey. With. Notes on the Microscopical Appear- 

 ances, by Professor Hull, F. R. S. 



[Eead, June 24, 1878.] 



Paet I. 



Happening to visit Carnmoney Hill, near Belfast, during the Meeting 

 of the British Association in 1874, I was much struck with the 

 abundance in the basalt of a mineral which I had never before noticed 

 in any of the basalts of the north of Ireland, and which I had reason 

 to believe then, and still consider to be, somewhat new to Irish 

 mineralogists, in so far that its composition and physical characters 

 have not yet been described. It may have been observed before, but 

 there is no description, at all agreeing with its characteristics, pub- 

 lished. 



The basalt in which this mineral occurs forms the old neck of a 

 Miocene volcano. It is massively columnar, the columnar structure 

 being, however, horizontal, not vertical, as is usually seen ; but in 

 all respects similar to what may be observed in large dykes or other 

 masses of intrusive basalt. The rock itself is a rather coarse-grained 

 <lolerite ; extremely vesicular and amygdaloidal, possesses a very high 

 density, and is magnetic, affecting the needle very strongly — zeolites 

 are not abundant, but the cavities are filled, or in some places only 

 coated, with a peculiar black mineral which is the subject of the 

 present notice. 



In some cases this mineral entirely fills up the cavities, and 

 throughout the rock it appears in great profusion ; but in many places 

 where the amygdaloids are only partially coated with it, the remain- 

 ing space is filled with calcite — and occasionally apparently arrago- 

 nite — for sometimes the crystals have a radiated structure which 

 resembles that of a zeolite. 



The black mineral from this locality has, I believe, never been 

 hitherto described or analysed. On examining the maps of the Geo- 

 logical Survey I find the basalt is noted by the late Mr. Du Noyer as 

 ^ ' black basalt, highly crystalline ; cellular cavities lined with pitch- 

 stone," for which he evidently mistook this mineral. And in the 

 Geological Survey collections in the Museum of the College of Science, 

 Dublin, specimens from this place are labelled " Yesicular basalt, with 

 obsidian." However, the peculiar softness of the mineral pre- 

 cludes this idea at once. There are two minerals to which it bears 

 a distant resemblance. In physical characters it somewhat agrees 

 with the chlorophaeite of Macculloch, so far as colour, specific gravity, 

 and hardness. But its chemical properties are totally different, as 

 will be seen further on — that is, if we can rely upon the analyses of 



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