ALUMINA. 373 



At Hustis' farm, in Phillipstown, there are lead-coloured crystals, associated with serpen- 

 tine in white limestone. 



On the farm of T. Foster, in the town of Southeast, it occurs in small plates or flattened 

 crystals of a green colour, associated with hornblende, serpentine and magnetic iron ore. 



St. Lawrence County. Eight miles from Potsdam, on the road to Pierrepont, black mica 

 has been found in plates of seven inches in length. 



At Pope's mill on Fish creek in Morristown, mica has been obtained in six-sided crystals 

 of a copper colour, sometimes six inches in diameter. The prisms are usually tapering, and 

 someiimes have the plates bent or curved. 



A mile southwest of the village of Gouverneur, silvery mica occurs in the white limestone. 

 In the same town, the copper-coloured variety, in plates of considerable size, is often met 

 with. 



In the town of Rossie, two miles north of Somerville, there is a beautiful copper-coloured 

 mica, associated with a buff serpentine in white limestone. 



One of the finest localities is in the town of Edwards, where it occurs abundantly in crys- 



Fig. 396. tals which are six-sided, or exhibit sections of this form. It 



^^^'\- is of a dark bronze-colour, transparent in thin lamins. The 



^,^^x. ^\ sides incline to each other at angles of 119° and 121°. The 



<^\ '"•.., |\ laminae are often much bent or twisted, and they are of vari- 



^x^ """•-., ]^^ ous sizes from an inch to six inches in diameter. Fig. 396 is 



\s.^ ^.^^ another form common at this locality. 



^•^^ Tliere is also in the same town a beautiful silvery mica, 



which exhibits the same regular outline, and affords the finest specimens of this variety here- 

 tofore found in the State. 



Saratoga County. In the town of Greenfield, about a mile north of Saratoga-Springs, 

 handsome crystals and irregular plates of a reddish brown colour are found associated with 

 feldspar, chrysoberyl, garnet and tourmaline in a vein of granite. This mineral has an un- 

 commonly fine .lustre ; and the crystals, when viewed across the axis, have a rich oil-green 

 colour. 



The form represented in Fig. 388 has been observed at this locality. Many of the plates 

 exhibit a beautiful star-like arrangement. 



In some cases, small scales or crystals of mica are arranged in a plumose manner, and 

 have the appearance of filaments of amianthus. This variety has been called Prismatic mica. 



Washington County. Mica of a dark colour is found associated with pyroxene or hyper- 

 sthene, on the banks of Lake George, about two miles south of Ticonderoga in the town of 

 Putnam. 



Westchester County. Mica is common in the gneiss rock in this county. 



On the Croton aqueduct, near Yonkers, it is often crystallized in rhombs and in six-sided 

 tables of a greyish brown colour, and having a beautiful lustre. It has a cleavage parallel to 

 the shorter axis of the crystals, as in Fig. 390 ; and this is sometimes so marked, that very 

 narrow plates or threads may be detached, resembling fibres of asbestus. At New-Rochelle, 



