Notices of Trappean Minerals. 55 



in similar rifts in. the greenstone at Bergen Hill. I have also 

 found the same mineral, although less distinctly characterized, 

 in the greenstone at Piermont, the terminus of the New York 

 and Erie railroad. This mineral occurs in veins of various de- 

 grees of thickness, from an inch to that of a mere coating on the 

 greenstone to which it is attached. In every case, however, the 

 mass is made of fibres or crystals the form of which cannot be 

 exactly determined, usually radiating from various centres, and 

 interlacing each other in an irregular manner. Sometimes these 

 fibres are parallel, when the mineral bears a resemblance to the 

 nemalite of Nnttall. When the bundles of fibres are broken up, 

 they separate into needle-form crystals, which are exceedingly 

 sharp. These needles are tough, and when subjected to the 

 pestle appear like amianthus. The same amianthoid appearance 

 is exhibited by many of the specimens found at the locality, a 

 change which may perhaps be referred to atmospheric agencies. 



Color snow-white. Lustre silky, shining. Translucent. Hard- 

 ness about 3. Specific gravity of a closely aggregated specimen, 

 2.836. 



Alone before the blowpipe, our mineral fuses readily, even when 

 in quite large fragments, and with slight bubbling, into a beauti- 

 ful white enamel. With borax it melts into a transparent glass. 

 It gelatinizes with muriatic acid. When heated to redness in a 

 crucible, it forms a porcelainous mass from partial fusion. Accord- 

 ing to my analysis, the following is its composition, in one hun- 

 dred grains, viz. 



Silica, ...... 54.60 



Lime, 33.65 



Magnesia, ...... 6.S0 



Oxide of iron, with a little alumina, . 0.50 



Water and carbonic acid, . . . 3.20* 



Our mineral differs from the stellite of Dr. Thomson in its con- 

 taining less alumina, oxide of iron, and water ; but these may, 



* The composition of the Scotch mineral, according to Dr. Thomson, is as fol- 

 lows, viz. 



Silica, .' 48.465 



Lime, 

 Magnesia, 

 Alumina, . 

 Proto.\ide of iron, 

 Water, 



30.260 

 5 580 

 5 301 

 3.534 

 6.108 



