348 NEW YORK STATE MUSEUM 



states that the ore is cut off on the north by a trap dike. The ore is 

 pyritous and is no longer mined. The breast was 8-10 ft. The 

 hanging wall is gneiss and contains microperthitic orthoclase, quarrz, 

 green biotite, magnetite and pyrite. 



The Cheever Mine. A general section of the Cheever ore body 

 is here given. The mine is situated about two miles north of Port 

 Henry, but the ore belt is prolonged about a mile further in a north- 

 erly direction, the Goff mine being in this portion. The Cheever is 

 one of the most interesting of all in its geology, and for tins reason the 

 geological section has been prepared based on the outline of the ore 

 body given by Mr Putnam (10th Census Yol. X. p. 113). The upper 

 topography is reproduced from the 20 ft. contour map of the U. S. 

 Geol. Survey and from sketches made on the ground. The section 

 shows that the ore has over it gray feldspathic gneiss 25' containing 

 green pyroxene, plagioclase, quartz and orthoclase. The lean ore 

 consists of magnetite with some green pyroxene and some plagioclase. 



The next 15' is hornblendic gneiss, containing quartz, microper- 

 thite, plagioclase, orthoclase, brown hornblende, green pyroxene, 

 garnet and apatite. Fifty yards from the ore is gray gneiss again, 

 with quartz, microperthitic orthoclase, brown biotite, very little 

 plagioclase, and magnetite. Over this lies black hornblendic schist 

 and white crystalline limestone. Under the ore is gneiss again but 

 50 feet east of the ore body, foliated gabbro appears consisting of 

 bastite, brown hornblende, and plagioclase represented by a saus- 

 suritic alteration product. The bastite is a light yellow, feebly 

 rjleochroic, brightly polarizing mineral, very fibrous and with extinc- 

 tions parallel to the fibres. In the longitudinal sections it shows the 

 trace of a biaxial figure, but in one transverse section a rectangular 

 cleavage still remained with diagonal extinctions. This would sug- 

 gest diallage as the original of it. A few garnets are also present. 

 A little further the gabbro becomes massive," and contains hyper- 

 sthene, brown hornblende, magnetite, much garnet and shattered and 

 saussuritic plagioclase. The gabbro extends to the lake. To the 

 west the ore is cut off by a fault, the underlying gabbro being 

 heaved up along the west side. The ore is also cut by several trap 

 dikes all of the diabase type, which upset it short distances. The 

 ore body is not one single continuous bed, but splits at times into 

 two from incoming horses. 



