Report on the projected Survey of the State of Maryland. 13 



These two varieties of iron ore, are the ochrey red oxide of iron (red 

 ochre) and the ochrey hroiun oxide of iron, (yellow ochre.) 



The estimate of the value of red and yellow ochres produced at 

 Baltimore and exported, exceeds two thousand dollars a year. By 

 the production of these articles within our own limits, the importation 

 has been entirely excluded ; and the domestic articles are now fur- 

 nished at one half of their former prices. 



But a still more valuable constituent of the tertiary formation of 

 Maryland is the deposite of those ores of iron which are used for the 

 extraction of the metal. Notice has alreade been taken of the hos- 

 ore of the Eastern Shore. The same variety is found on the West- 

 ern Shore, as in the neighborhood of Queen Anne, in Prince 

 George's county, &.c. 



Those kinds of iron ore, which are the most valuble are described 

 in systematic works under two specific heads ; namely, carbonate of 

 iron and brown oxide of iron. The varieties, included under these 

 two heads, occur throughout a broad belt of country comprising the 

 upper limits of the tertiary formation, where it is associated with a 

 coarse gravel, ferruginous sand, transported boulders and blocks — 

 constituting what in some systems of geology is termed the Erratic 

 block groupe, and which with us is found to rest immediately upon 

 the primitive or primary rocks. These ores of iron (usually but im- 

 properly classed among the argillaceous oxides of iron, that belong 

 to another epoch) are found occurring in nodules of an oval or spher- 

 ical form, sometimes kidney-shaped, and composed of concentric 

 layers. The nodules frequently embrace a nucleus, differing in 

 density and color from the exterior layer. The texture of this ex- 

 terior layer is compact, but its density diminishes towards the centre, 

 and while its color is commonly dark brown, that of the central por- 

 tion is light approaching to yellow. The technological terms ap- 

 plied to these varieties of iron ore are brown ores and hone ores — 

 names which have reference to their physical characters. 



All these ores belong to the mineralogical species, carbonate of 

 iron. But when the nodules contain cavities, as they frequently do, 

 these are lined with minute crystals of a rich velvety aspect ; which 

 are hydrated oxide of iron, a variety of the species brown oxide of 

 iron. 



They are ranked among the best ores of iron — working easily and 

 yielding an average of metal from forty to fifty per cent. A cele- 

 brated deposite of them is in Prince George's county at Snoivden^s 



