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The porphyry at the east side of Browndod in an old excavation on 

 the road side, has a reddish brown basis, containing embedded in it small 

 concretions of smoke quartz, with earthy and glassy crystals of reddish 

 felspar and olivine. At the Tardree quarries the felspar is white ; to 

 the east of this the rock is much weathered at the surface, its decompo- 

 sition giving rise to a sandy soil, from which the district on the north- 

 east is called Sandy Braes. 



At Barnish, half-a-mile to the east of the great Tardree quarry, the 

 porphyry in one of the pits is constituted of horizontal layers of diffe- 

 rent colours from three inches to three feet in thickness. There are 

 layers of red, layers of gray, and layers of white interstratified, if I 

 may so call it, in a crystalline rock with each other. The whole of the 

 decomposing rock in the pit is in a condition easily reducible to sand. 

 This sand is used by the country gentlemen for the walks in their pleasure 

 grounds. By a little care in the pit, the red sand can be put in a heap, 

 the white in a heap, and the gray in a heap, and thus a gentleman may 

 have red walks, gray walks, or white walks, according to his taste ; and 

 this is not unusual for some miles from this place. 



On seeing this pit the idea suggested itself that it is possible those 

 layers of different colours may once have been some of the red and gray 

 slates so usual in the old gray wacke rocks, altered from the dull argilla- 

 ceous stony aspect of the clay slate to a highly crystalline state, now 

 easily decomposed into sand without altering much the colour. The level 

 layers and the varieties of colour would both lead to this conclusion. 



Dubourdieu, in his Statistical Survey of the county of Antrim, says 

 that "Pitchstone porphyry and pearlstone porphyry occur in parts of 

 this district. Two large masses of each variety may be seen a few yards 

 below the bridge across the Loon Burn on the road from Connor to 

 Doagh. In the pitchstone porphyry the sound part in the interior is 

 bluish black and has a shining and vitreous lustre ; the surface weathers 

 yellowish green of different shades, according to the advance of decay ; 

 common opal occurs in it, either in plates or small veins. In the pearl- 

 stone porphyry the colour is smoke gray, or bluish, with a pearly lustre; 

 it is formed of very thin concentric coats." 



I went to Loon Burn, but was much disappointed : I saw no such 

 large masses as Mr. Dubourdieu described — nothing that I would call a 

 dyke. There is in a sandpit 20 yards below the road, and 30 yards south 

 of the stream, a black string two inches thick, which might in depth 

 become thicker. It has, indeed, that appearance, but the rock on both 

 sides of it is in a decomposing state — in fact coarse brown sand passing 

 into the harder black rock, that it is no easy matter to say what was the 

 original thickness. I may, I think, safely say there is no such dyke 

 visible there now ; either the dyke has been decomposed and grass or 

 furze grown over the place, or the original description was greatly 

 exaggerated. 



All the porphyry about Loon Barn shows an unusually coarse condi- 

 tion of crystallization. In a decomposing state it can be raised in sand, 

 the particles of which are as large as peas. 



