J?38 Dr Colquhoun on th£ Argillaceous Ore of Iron. 



1. A very flat nodule, found imbedded in schist at Cross- 

 basket. Colour of the fractured surface, hair-brown. Frac- 

 ture fine-grained, somewhat uneven. Hard : scratched by 

 the knife. The nodule is enveloped by a thin yellowish-co- 

 loured ochraceous looking crust, which has evidently been 

 produced by the decomposition of the carbonate of iron. It 

 was composed of 



Carbonate of protoxide of iron, . . 80.70 



Argillaceous matter, with a little carbona- "I -in A^f 



ceous matter, .... / * 



Carbonate of lime, . . . . 2.19 



Carbonate of magnesia, moisture, and loss, 6.66 



100.00 



This nodule was found in the immediate vicinity of a regu- 

 lar stratum of ironstone. The ore composing this stratum had 

 a greyish-black colour ; it broke with a fine-grained, earthy, 

 somewhat uneven fracture ; and consisted of 



Carbonate of protoxide of iron, . 60.34 



Argillaceous matter, 'with a little carbona- ) 

 ceous matter, . . . j 



Carbonate of lime, .... 1.87 



Carbonate of magnesia, moisture, and loss, 6.99 



100.00 



2. A nodule brought from the vicinity of Crossbasket, 

 where many similar ones occur in a stratum of indurated clay 

 (Jire-day) from which this specimen was taken. They are 

 generally small, and vary from an inch to four inches in diame- 

 ter. They are smooth and rounded externally. They break 

 with a fine earthy fracture, and the colour of the fractured sur- 

 face is yellowish-grey. The specimen proved to be composed of 



, Carbonate of protoxide of iron, . . 90.15 



Insoluble clayey matter, . . . 6.30 



Carbonate of lime, . . . 1.09 



Loss, . 2.46 



100.00 



