ALUMINA. 343 



gravity 2.612. Before the blowpipe, it fuses into a beautiful white enamel. With carbonate 

 of soda, it fuses with effervescence into a transparent white bead. "With borax, it fuses into 

 a perfectly transparent glass when the quantity of stellite is small ; if it be larger, the bead 

 exhibits a silica skeleton. It forms a jelly with muriatic acid. 



From Thomsonite, which it often closely resembles, Stellite may be distinguished by the 

 blowpipe characters. Its composition differs very much from that of many of the zeolite 

 family. i 



Composition. Silica 48.46, lime 30.96, magnesia 5.58, alumina 5.30, protoxide of iron 

 3.53, water 6.10 {Thomson). The formula CaSSiOs will probably express the composition 

 of this mineral. 



Geological Situation. This mineral has heretofore been observed only in rifts in green- 

 stone. 



LOCALITIES. 



Rockland County. A mineral agreeing very well in its characters with the stellite of 

 Thomson, is found in the rifts of greenstone at Piermont. The fibres are sometimes radiated ; 

 at others they are straight, when the mineral resembles the nemalite of Nuttall, but the blow- 

 pipe characters will at once distinguish it. 



This mineral is believed also to occur in the greenstone bowlders in New- York and West- 

 chester, where it has probably been mistaken for Zeolite, a name now rather applicable to a 

 family of minerals than to a particular species. 



The finest specimens, however, have been found at Bergen hill in New-Jersey. They are 

 in the form of groups or congeries of needle-form crystals, which are exceedingly sharp. 

 These needles are tough, and when subjected to the pestle, appear like amianthus. The 

 specific gravity of one of the purest specimens is 2.836. Before the blowpipe, it fuses 

 readily, with some effervescence, into a white enamel. The composition of a specimen from 

 this locality is as follows, viz : 



Silica, 54.60 



Lime, 33.65 



Magnesia, 6.80 



Oxide of iron, with a little alumina, 0.60 



Water and carbonic acid, 3. 20 



In chemical composition, our mineral differs from the stellite of Dr. Thomson, in its con- 

 taining less alumina, oxide of iron and water. But these may after all be accidental ingre- 

 dients. It closely resembles woUastonite, except that the latter has soda as one of its con- 

 stituents. It differs from natrolite, in the small quantity of alumina which it contains. 



