SILICA. 305 



crumbled down, and left these crystals and the veins of asbestus exposed. Some barrels of 

 asbestus have been obtained from Rogers' farm, a mile from Patterson. By macerating the 

 specimens in dilute muriatic acid, the dolomite is dissolved, and the asbestus is left in the 

 form of white silky fibres closely interlaced. 



The variety amianthus, in thin seams, traverses the serpentine at Hustis' farm in Phillips- 

 town, five miles south of the village of Fishkill, on the stage road to New-York. It is white 

 and yellowish while, and has a beautiful silky appearance. The fibres are fusible by the blow- 

 pipe, aiter coiling at the extremities, into a white opaque mass ; they arc readily fusible with 

 borax. This mineral has been thought to be identical with the foreign picrolite ; but the latter 

 is still an obscure species. 



At Cotton Rock, on the bank of the Hudson in Phillipstown, about three and a half miles 

 below West-Point, between high and low water mark, beautiful specimens of asbestus have 

 been obtained. The rocks here, according to Mr. Mather, are impure verd antique, serpentine 

 with diallage rock, augite and granite. Veins of asbestus and delicate silky amianthus pass 

 through the serpentine ; the latter having the appearance of cotton or raw silk, has given rise 

 to the name by which this locality is known.* 



Richmond County. The varieties, asbestus and amianthus, are very abundant in various 

 parts of this county, especially near the Quarantine. They are found associated with com- 

 mon and steatitic serpentine, and other magnesian minerals. The hard asbestus, resembling 

 chips of wood, occurs near the Pavilion hotel ; it breaks into rhombic prisms liaving the form 

 of liornblcnde. In the same vicinity there is rose straw-coloured amianthus, having the 

 fibres between two and three feet in length. Tliese fibres have the lustre and softness of silk, 

 and may be spun or woven. As a locality of these varieties, this is one of the best in the 

 United States, and is thought to be equal to any hitherto discovered. It was first made known 

 to mineralogists by Mr. J. Pierce.f 



Rockland County. Small but imperfect crystals of black hornblende are common in the 

 trap at Haverstraw, and in other parts of this county. The lamellar variety is abundant at 

 Stony point ; and actynolile of a dark green colour, the fibres being radiated, interlaced and 

 imperfectly crystallized, occurs two and a half miles west of Grassy point, associated with a 

 kind of serpentine marble. This locality is often known by tlie name of Montague's marble 

 quarry ; but it is of little value, except for the cabinet specimens which it aflbrds. 



Asbestus or picrolite is found in thin veins, associated with the soft serpentine or kerolile, 

 in the trap dyke on the north side of Stony point. It has a greenish colour, a high silky 

 lustre, and the fibres are extremely delicate. 



* Mather. NtwYork Geological Rrports, ISjy, ^ American Journal of Science. I. 51. 



MiN. — PartII. 39 



