494 



Report of the State Geologist. 



the limestone. About two miles south from this locality, towards the centre 

 of the gneiss area, the road crosses a small patch of limestone only a few rods 

 square, entirely enclosed in gneiss. It would be difficult to account for this 

 as anything but an inclusion in an igneous rock, and that it is such, is further 

 indicated by the fact that it is tilled with contact minerals. Thus, the gneiss 

 area between the Edwards and the Pitcairn limestone belts shows evidence on 

 both its northern and southern boundaries, as well as towards the centre, that 

 it is in part of igneous origin and intrusive in the limestone. The character 

 of the gneiss throughout the area is such as to render it highly probable that 

 this is true of the greater part of the rock. 



About two miles east of the village of Colton, near the town line of 

 Colton and Parishville, the gneiss and limestone are shown almost, but not 

 quite, in absolute contact. The structural relations are not such as to suggest 

 conformity but rather the reverse, while near the contact the limestone is cut 

 through and through by a pegmatitic intrusion. A characteristic contact zone 

 is present, showing coccolite with titanite, tremolite, etc., and the pegmatite 

 contains irregular masses of the same composition, doubtless inclusions of 

 altered limestone. The position of the pegmatite is such as to suggest that it 

 may be a secretion of a plutonic magma represented by the adjacent gneiss, 

 and this idea is greatly strengthened by the fact that the gneiss itself contains 

 coccolite masses precisely like those in the pegmatite, and very difficult to 

 explain as anything but inclusions of altered limestone. The phenomena here 

 are not conclusive but have value in connection with the facts shown at other 

 localities. Within a mile north of this point there are several recurrences of 

 structural relations suggesting intrusions, but showing no contacts. At one 

 point, however, which must be almost, if not exactly, on the contact, limestone 

 is shown with abundant large crystals of altered pyroxene, with othei 

 products characteristic of contact action. An analogous case is shown in 

 Hermon, where, though no actual contact is shown, there is, just on the line 

 where the gneiss and limestone should meet, a mass of scapolite, pyroxene 

 ami other contact minerals. 



The gneiss area north of Gouverneur village shows phenomena somewhat 

 similar to those near Colton. No contact is shown, but the limestone in the 

 neighborhood of the gneiss is often broken through by pegmatite. In this 

 <-;i>c rln' limestone shows little or no alteration, but the pegmatite itself 

 becomes rich in titanite near the contact. The gneiss of this area also show s 

 abundant examples of the black inclusions, and of passage into wholly massive 

 phases. 



