MINERALS OF MARYLAND. 103 



ferruginous sandstone, which passes into a coarse conglome- 

 rate, composed of siUceous pebbles with a ferruginous cement. 

 Bog iron ore forms extensive deposites in the northern parts 

 of Somerset and Worcester counties; indeed its formation is 

 still in progress. It is smelted at the Naseongo furnace. 

 Phosphate of iron occurs in crystals lining the cavities of the 

 bog ore, and of course impairs the quality of the metal. 



Sulphate of lime in crystals is found in many places, but 

 most frequently within the tertiary region. An interesting 

 locality occurs on St. Mary's river, in a bed of clay of a bluish 

 gray colour and very siliceous. The upper portion of the clay 

 abounds with fossil shells, above which there is a considerable 

 covering of ferruginous sand and gravel, containing lignite and 

 iron pyrites. The spontaneous oxidation of the latter pro- 

 duces sulphate of iron, which in its descent by percolation is 

 decomposed by the carbonate of lime of the shells, and pro- 

 duces the groups of crystals of sulphate of lime, which are 

 mostly to be seen below the shells. Near the mouth of the 

 Patuxent, there is another and similar natural factory, but the 

 form of the crystals differs. Those on the St. Mary's river 

 are all grouped together at one of their ends ; frequently eight 

 or ten of them in a group are so arranged as to radiate from a 

 central point, and the flattened prism sometimes six or seven 

 inches long is lessened in thickness outward from the radiating 

 point so as to assume a lanceolate form. The Patuxent 

 specimens are grouped in a similar manner, but the prisms 

 are shorter, more perfect on their sides, and are concave on 

 their outer terminations. 



Quartz is found frequently constituting the casts of fossils, 

 both animal and vegetable, and is usually of a coarse impure 

 variety ; but in one locality Professor Ducatel met with a 

 specimen of silicified wood, partly composed of fine blue 

 chalcedony. 



Amber* exists at Cape Sable on the Magothy river. 



Lignite at the same place; and also, 



Sulphuret of irofi, which in connection with the lignite 

 forms an extensive deposite and furnishes the material for a 

 large manufactory of alum and copperas. The amber is 



* Dr. Troost. 



