478 Elements of Mineralogy. 



I. VARIETY. 

 High land Argillaceous Ores. 



Miner a fern Ochracea. 



20. Thefe are either yellow, red, brown> 

 or greyifh, indurated and friable, or loofe 

 and powdery, or in grains ; they confift 

 chiefly of the red or yellow calx of iron, or 

 of the grey iron ore, or torjlen in a loofe 

 farm, mixed with argill or clay, and confe- 

 quently often contain manganefe, or fiderite y 

 and fome, particularly in France, and the 

 neighbourhood of Liege , are faid to contain 

 the calx of zinc. Hence there are many 

 varities of them, and their yield of iron, as 

 well as its qualities, are very different : they 

 do not effervefce with acids, (unlefs calca- 

 reous or muriatic earth be cafnally mixed with 

 them,) and are difficultly foluble in them; 

 the rnoft foluble are the beft; they never 

 obey the magnet before calcination, and rarely 

 after it. 



21. Horn-ftone over- loaded with iron be- 

 longs to this fpecies. 



22. Mr. Rinman mentions a 'white iron 

 ore found in Kent y mixed with clay or marl, 

 %hich affords 47 per cent, of brittle iron, 



and 



