Dr Colquhoun on the Argillaceous Ore of Iron. 237 



lour is brown. Fracture, fine-grained, earthy ; rather uneven. 

 Tough, and difficultly pounded; communicating a feeling of 

 elasticity under the pestle. Rather hard ; scratched by the 

 knife. Adheres slightly to the tongue, a property which did 

 not appear to be possessed in a sensible degree by any of the 

 seven ores already described. Sp. gr. 3.0553. Numerous 

 bivalve shells, of a pale wood brown colour, occur scattered 

 through the mass of this ore, and form a strong contrast with 

 its darker shade. ' This is one of the most. valuable iron ores 

 of Scotland, where it is familiarly known under the name of 

 Black Ironstone, or Mushefs Black Band. The latter appella- 

 tion has been given from the circumstance that it was first 

 smelted by Mr Mushet, to whom we have already referred as 

 the metallurgist most distinguished for his practical skill. * 



It lies about fourteen fathoms below the fifth Glasgow coal 

 bed, or splint coal ; and constitutes a layer about fourteen in- 

 ches in thickness. It is remarkable that it has hitherto been 

 found nowhere except in the neighbourhood of Airdrie : al- 

 though several attempts have been made in other localities to 

 reach it by boring. At the Clyde Iron Works it is justly re- 

 garded as the richest and most valuable ore which they at pre- 

 sent possess. 



(L) From a stratum situated in the vicinity of Crossbasket. 

 Colour bluish-grey. Fracture in the great even : in the small 

 very fine-grained, earthy. Rather hard. 



Such was the composition and the mineralogical details of 

 various specimens of ironstone which were obtained from com- 

 ponent strata of the independent coal formation around Glas- 

 gow. But it is well known that this ore presents itself not 

 only in uninterrupted strata or hands, as the the miners term 

 them, but also in the form of independent nodules or balls, 

 imbedded in a stratum of some foreign mineral. We shall 

 subjoin a few analyses of these nodules. The analyses were 

 made with a less scrupulous accuracy than those of the band- 

 ironstones, but still, it is hoped, with sufficient care and atten- 

 tion to permit the results to be relied on as exhibiting the 

 true mineralogical character of this variety of the ore. 



• He has also given a particular account of this ore in the Philosophical 

 Magazine, vol. iii. p. 254. 



