REPORT OF THE DIRECTOR AND STATE GEOLOGIST 1903 191 



Warwichj Orange co. A small outcrop of serpentine shows an 

 association of magnesite in places. 



Stony Point, Rockland co. Occurrence similar to that at War- 

 wick. 



6 Mica. Three distinct minerals are included commercially 

 under this head. They are: 



1 Muscovite or white mica, ordinarily known as isinglass 



2 Biotite, or black mica 



3 Phlogopite, or amber mica 



Chemically the micas are all silicates of magnesium and alu- 

 minum ; the black and amber micas also contain iron. Muscovite 

 is extensively used in the doors of stoves and furnaces and for 

 lamp chimneys, where its transparency and resistance to heat 

 render it particularly valuable. Recently muscovite and phlogo- 

 pite have been utilized as insulating material in electric appara- 

 tus, particularly for the armatures of dynamos. Ground mica, 

 which is classed commercially as " scrap mica '' as distinct from 

 " sheet mica " described above, is used in the manufacture of 

 wall paper. Mica is a common constituent in many of the rocks 

 of New York and occurs in sheets in several localities. 



Warwick, Orange co. Eight miles southweist of Warwick near 

 Greenwood lake, muscovite occurs in a feldspar vein in plates 

 sometimes a foot in diameter. 



Monroe, Orange co. A deposit of greenish mica occurs in 

 augite rock near Mombasha pond. The mineral is found in good 

 sized plates and is now being mined. 



Both muscovite and phlogopite are found in plates of varying 

 size throughout Orange co. in the granite and gneiss rocks and 

 at the contact of these rocks with limestone. 



Pleasantville, Westchester co. A deposit of mica was at one 

 time opened and mined at this locality, but has been abandoned. 



Henderson, Jefferson co. A yellow, somewhat copper-colored 

 mica, probably phlogopite, occurs in large plates near Hender- 

 son. 



• Pierrepont, St Lawrence co. At a point 1 mile north of Pierre- 

 pont muscovite occurs in plates which are often 7 inches across. 



