

AliRAN. GEOLOGY. PITCHSTONE. 423 



12. Grey muddy green, granular, and glistening ; but 

 the fracture passing to conchoidal with a dull surface ; 

 when it puts on the aspect of chalcedony. 



13. Obscure yellow green; breaking by the first frac- 

 ture into conchoidal concretions with a smooth dull sur- 

 face. These, being again broken, present a granular 

 glistening fracture. This is a sub-variety of the former. 



14. A mixture of chalcedonic chert and pitchstone, so 

 intimate as to resemble a transition between the two till 

 examined by the magnifying glass. 



15. Simple granular-conchoidal, brownish green passing 

 to brown, and presenting different sub- varieties. 



16. Large granular, slightly conchoidal, of a yellowish 

 brown colour. 



17. Brownish black, small conchoidal-granular, and obr 

 scurely porphyritic. 



1 8. Black, with a large flat conchoidal fracture ; sprinkled 

 with minute spots that appear at first sight to be im- 

 bedded substances, but are discovered by the lens to 

 be small squamous fractures independent of the ge- 

 neral one. 



19. Black; the conchoidal and large granular fracture 

 united ; with rare and imperfect crystals of white glassy 

 felspar. 



20. Black and dark grey alternating in stripes, re- 

 sembling in this respect some varieties of obsidian; 

 minutely porphyritic, with a very large and perfect con- 

 choidal fracture resembling that of glass. 



21. Passing into a brown substance (hornstone of some) 

 apparently intermediate between pitchstone and chalce- 

 dony, and interlaminated with dry chalcedony, (or chert,) 

 and quartz. Botryoidal translucent chalcedony occurs hi 

 rifts in this variety. This transition is found in one of the 

 veins at Tormore. 



22. A transition into yellow brown chalcedonic chert, 

 the hornstone of many authors. 



