110 MINERALS OF MARYLAND. 



Talc is most common in the dolomite. 



Tourmaline^ brown and yellow are occasionally seen. 



Tremoliie, white, in fibrous and radiated masses is common. 



Asbestiis, a seam or vein of this substance, extending for 

 many yards, from 1 to 4 inches thick, in dolomite, was ex- 

 posed recently by the excavations for the Susquehanna rail 

 road. It is perfectly white and its fibres remarkably fine and 

 soft. 



Augile, in white and grayish white crystals, rarely perfect, 

 is very abundant in the dolomites. I have part of a crystal, 

 (being as usual a flat prism) which is Ai inches long and 21 

 inches broad. 



Red oxide of titanium^ in crystals, is occasionally seen. 



Fetid, felspar^ semi-transparent, occurs in a fine grained 

 limestone, at Scott's mills. 



Sulplmret of iron, in crystals, is often dispersed through the 

 dolomites, and large pentagonal dodecaedrons are occasion- 

 ally seen. 



Graphite occurs sparingly. 



The serpentine and associated tales enter the northern boun- 

 dary of the State, a few miles west of the Susquehanna river, 

 and are apparently in isolated and independent portions in 

 gneiss and mica-slate. They are generally in a line running 

 south-westerly through the State to the Potomac river, a little 

 west of Rockville. It is probable that they are intrusive rocks, 

 but have not been sufficiently investigated to permit more than 

 a mere suggestion that such may have been the case. This 

 formation embraces a variety of interesting minerals, which 

 will be adverted to. 



Serpentine, both common and precious, (the latter most 

 abundant near Gooptown) and of a variety of colours; it 

 is opaque or translucent. 



Diallage, in lamellated masses, in all the localities. 



Talc, in every variety, but rarely in distinct crystals. The 

 finest specimens are the lamellated masses near Gooptown, 

 which present every shade of purple, rose colour, blue, and 

 green. 



A beautiful translucent variety of a delicate apple green 

 colour and foliated, occurs in serpentine, on the Gunpowder 

 river, 23 miles north-north-east from Baltimore. 



