360 [ proc - B.N.F.Cv 



Antrim, gave rise to remarkable varieties of rhyolite and pitch- 

 stone, many of which are found in the Tardree district. Von 

 Lasaulx and Professor Cole regard the dome of Tardee mountain 

 as a volcanic core, from which true lavas flowed, forming the 

 plateaux to south and north. 



The members started by the 9-55 a.m. train from Belfast to 

 Ballyclare, where they were met by Mr. J. Strachan, who kindly 

 acted as conductor. On arrival at the Sandy Braes plateau, the 

 conductor pointed out the yellow, pink, red, and black banded and 

 fluidal pitchstones, and the spherulitic nodules of silicified rhyolite 

 filled with opal and chalcedony. Only a few of these nodules were T 

 however, obtained. The perlitic types of rhyolite found on Sandy 

 Braes are very beautiful, and similar in character to the recent 

 rhyolites of Hungary. Under the microscope they show a glassy 

 base with perlitic structure, and phenocrysts of quartz, sanidine, and 

 magnetite. From Sandy Braes the drive was continued to the 

 North Quarry on Tardree Mountain, and here in a small portion 

 of the quarry, at the extreme north end, Mr. Strachan pointed out 

 a red stony rhyolite, worked at present ; and in the main part of 

 the quarry, now disused, he drew attention to the apparently 

 massive columnar structure. Shortly after leaving this, the cross- 

 road to the north was taken, and a quarry beside it of banded 

 lithoidal rhyolite, of a pink colour, with yellow layers and 

 undulating flow planes, was examined and photographed. 



Returning, the South Quarry on Tardree was next visited, and 

 the apparent massive columnar structure, similar to that of the 

 North Quarry, was noted, the rock being divided by upright 

 parallel joints into parallel sheets, the edges giving the effect of 

 columnar structure. Specimens of small true columns, about six 

 inches square, were, however, obtained. The typical rock, a 

 lithoidal rhyolite, when freshly quarried, is of a purple grey colour, 

 which turns white on drying. Under the microscope it shows a 

 microcrystalline — sometimes nearly cryptocrystalline — base, with 

 phenocrysts of quartz and sanidine. Scales of tridymite have 



