of Boston and its Vicinity, 191 



Geological Situation and Localities* 



It ^^curs massive and disseminatecl in Quartz which traverses 



Greenstone, and in decomposing Grreenstone, at Charlestown 

 and Medforcl. 



A 



SPECIES y.^JVOnULAR IIWjYSTOXE. 



r 



Nodular Argillaceous oxide of Iron, Cleaveland^ p. 471* Reniform Iron 

 Ore, or Iron Kidney. Jameson^ vol. ii. p. 3i29. Nodular Ironstone, Airzrart. 

 vol. II. p. 178. Clay IronstonCj •Sikin^ p. 119. 



External Characters. 



Its colour is brown ;^ of which it occurs yellowish brown, 

 or uraber brown, and liver brown. The colours are of various 

 intensity in the same specimen, and are arranged in concentric 

 stripes. The uraber and liver brown colours are external, and 

 sometimes inclose a nucleus of a gall-stone yellow, or of a yellow- 

 ish grey colour 5 the internal are generally lighter than the ex- 



ternal colours. 

 It is dull. 



H 



It is opaque. 



It occurs in rounded and ovate masses, from the size of a hen's 

 to that of an ostrich's egg. 



It exhales an argillaceous odour when breathed upon. 



. It adheres to the tongue. 

 The streak is pearl grey, sienna yellow, and yellowish brown, 

 according to the colour of the part where it is made. 

 It is in concentrick lamella^ distinct concretions. 



It is semi-hard. 



C 



