300 



DESCRIPTIVE MINERALOGY. 



Fig. 224. 



Fig. 225. 



beautiful actynolite of a pale green colour, in a white talcose rock. It is in long slender 

 prisms both straight and bent, and intersected by transverse seams. 



Tremolite of a white and bluish white colour, is found in the white limestone in various 

 parts of the town of Dover. It is similar to that to be hereafter described as occurring in 

 New- York and Westchester counties. 



Essex Coijnty. There are localities of common hornblende in various parts of this county. 

 At almost all the mines of magnetic iron ore, it is one of the accompanying minerals. It is 

 usually black and massive ; sometimes it is white, has a high vitreous lustre, and is streaked 

 in the direction of the cleavage surfaces. Such specimens often occur at the Crag-Harbour 

 mine, near Port Henry. 



At Willsborough, nine miles northwest of the village of 

 Essex, small but perfect black crystals are imbedded in 

 black tourmaline. The forms are the triunitaire of Hauy, 

 Fig. 224 ; and the accelere of Haiiy, Fig. 225. M on * 

 152° IT'; M' on x 117° 43'; I on x 105° 11'; I on I 

 110° 2' ; r on r 149° 38' ; i on x 129° 8' (Shepard). 



Fine massive black hornblende, having a high lustre, is 

 found at the Barnum iron mine, about six miles west of 

 Port Henry. It forms a part of the walls of the mine. 

 The same variety also occurs near the locality of garnet 

 and tabular spar in the town of Lewis, 

 At the Sanford ore bed, in the western part of Moriah, 

 there is a variety of actynolite quite similar to that found in Orange county. And at another 

 mine having the same name, six miles west of Port Henry, veins of asbestus run through the 

 ore and the accompanying rock. 



Of the granular variety of hornblende, it is scarcely necessary to enumerate the localities, 

 as it is found at almost all the deposits of iron ore. 



Jefferson County. In the vicinity of Watertown, there are two varieties of tremolite. 

 The one is in the form of white translucent fibres, or bundles of fibres, which are variously 

 bent or divergent ; the other is dark brown, greyish brown and greyish white, and consists of 

 bundles of flat prismatic fibres which are bent and divergent. 



The variety amianthus occurs in thin veins, associated with serpentine, in the white hme- 

 stone near the village of Oxbow. 



New-York County. A beautiful white and bluish white tremolite is found in the quarries 

 of dolomite at Kingsbridge. In some cases it is in broad laminated masses, which have a 

 semi-crystalline structure and a high vitreous lustre, and is intersected by transverse seams. 

 Other specimens exhibit fasciculated groups of minute, diverging or interlacing fibres. It is 

 not unusual, in this and the adjoining county, to find the tremolite passing into pyroxene ; and 

 the purest specimens usually efiervesce slightly with acids, in consequence of the mixture of 

 dolomite. The foha of tremolite, occurring at Kingsbridge, are sometimes six to nine inches 

 in length. 



