400 Mr. Ainsworth ow the Metalliferous Veins 



ART. III. On the Geognostic Age of the Metalliferous Veins 

 of Lead/tills, Wanlockhead, and Glendinning, in the Counties 

 of Dumfries and Lanark. By William Ainsworth, Esq. 



An accurate opinion may be formed of the age of mineral veins 

 from a knowledge of the rocks in which they occur, and a study of 

 the phenomena of position, as also by a comparison of the riders or 

 veinstones, and accompanying fossils, with the simple minerals 

 which are met with in veins of the same character in different geo- 

 graphical situations. The latter, simply oryctognostic method, has 

 not received all the development of which it is capable, and pre- 

 sents difficulties which will only vanish before a very extensive 

 acquaintance with the products of different mineral veins. 



The vein-stones of the Leadhill and Wanlockhead mines, occur- 

 ing in the same formation, are nearly similar. They are quartz, 

 sulphate of barytes, calcareous spar, arragonite, sidero-calcite or 

 brown spar, and asbestus. 



The ores are lead glance, hydroxide of manganese, oxides of 

 lead, sparry iron-ore, calamine, brown iron-ochre, iron pyrites, azu- 

 rite (hydro-carbonate of blue copper,) carbonate of lead, phosphate 

 of leadj sulphate of lead, and fibrous hydrate of iron or brown hae- 

 matite. 



The veins are wrought for the lead glance alone. 



The vein-stones of Glendinning are quartz and calcareous spar ; 

 the ores, radiated gray antimony, brown blende, fine-grained lead 

 glance, and iron pyrites. 



If we compare these results with the mineralogical characters of 

 two other well-known metalliferous deposits, as those of the Hartz 

 and of the Pyrenees, we find the vein-stones at Clausthal to be 

 calcareous spar, quartz, and sulphate of barytes ; in the Pyrenees, 

 quartz, carbonate of lime, sulphate of barytes, and fluate of lime, 

 but the latter very rarely. 



Quartz accompanies veins of different ages. It is, however, most 

 abundant in the oldest veins of the intermediate series. It more 

 especially accompanies the various formations of lead glance with 

 native gold, or with silver, and lead glance with blende. It occurs 

 at Wanlockhead as a loosely -aggregated arenaceous rock, easily dis- 

 integrated by the hand. This is also the case in the Hartz. It is 

 the principal vein-stone of the mines of Laguore, (Pyrenees ;) but, 

 as a disseminated mineral, is wanting in almost all the transition 

 and metalliferous porphyries of Mexico. 



Sidero-calcite, — carbonate of lime, manganese, andiron, — accom- 

 panies calcareous spar and sparry iron-ore ; also quartz and sparry 

 iron-ore at Baigorry, in the Pyrenees. 



Sulphate of barytes and calcareous spar begin to accompany 

 veins of the middle age. The former was observed by Picot de la 

 Perouse in the mines of Baigorry, Aulus, &c.* 



* Journal de Physique, T. xxvi. p. 428. 



