Dr Colquhoun on the Argillaceous Ore of Iron. 221 " 



published as late as 1820, does not appear to give any ac- 

 count of the common compact argillaceous carbonate of iron 

 as a distinct mineral, although he describes the varieties of it 

 which Werner had enumerated under the heads of reniform, 

 lenticular, and jaspery ironstone. But even in his descrip- 

 tion of these varieties the professor has ascribed to them cha- 

 racters which can only belong to ores consisting essentially of 

 the peroxide of iron. * 



A predilection in favour of characteristics deduced from 

 external form, was probably the cause why this eminent mi- 

 neralogist, whose system has long been the manual of the 

 British student, allowed himself to overlook the most inte- 

 resting feature of this important mineral compound. A simi- 

 lar cause appears, in the case of this ore, to have misled the 

 illustrious French mineralogist Haiiy. For in the second 

 edition of his Traite de Mineralogie, (published in 1^22,) he 

 refers it, (under the names of/er oxide massifs fer oxide mas- 

 sif argilif ere, Jer oxide geodique,) together with an incongru- 

 ous assemblage of other minerals, for example, cubic and oc- 

 tohedral oxide of iron, hydrated oxide of iron, eisensinter, 

 &c., to one common species Jer oxide. These errors are in 

 Haiiy the less excusable, because at the period when his sys- 

 tem was published, the constitution of our ore must have been 

 familiarly known among the French metallurgists. And they 

 evince in a striking manner the paramount importance of a 

 close attention to the chemical constitution of minerals ; and 

 how imperfect a substitute for the want of this is, on some 

 occasions, supplied to the systematic mineralogist by any scru- 

 tiny of their external characters, even though it may be con- 

 ducted with consummate skill. 



^Ujj^ll those writers whom we have just enumerated may be 

 regarded as mere followers in the track of Werner, not one 

 of whom has correctly explored the nature of the argillaceous 

 carbonate of iron. And it becomes the more extraordinary 

 that this should be the fact, since, as far back as the year 

 1796, the distinguished German chemist Richter, published 

 an account of the analysis of six specimens of the ore, from 



* Vol. iii. p. 222, 224, 238. 



