138 -^'K^V YORK STATE ML'SEUM 



contact belts between the anorthosites and the other rocks t«.> the 

 eastward. They form irregular masses of a square mile or less 

 in area, and have revealed few details which would enable the 

 observer to describe them as laccoliths or inti-uded sheets, or st<xk.s. 

 They certainly do appear in dikes, and the larger masses display 

 characteristic irruptive contacts with the older rocks. 



The bodies of magnetite or of intermingled magnetite and il- 

 menite are merely phases of the gabbro, exceptionally enriched 

 with the iron-bearing minerals. There is no sharp demarcation 

 between so called ore and rock. All the rock has some ilmenite- 

 magnetite. All the ore^ contains some of the common minerals of 

 the reck, viz: olivine, pyroxene, and garnet, but the feldspar tends 

 to fail. Wq are compelled therefore to regard the ore bodies 

 simply as basic phases of the gabbro, exceptionally enriched with 

 one of its normal minerals. Details of these relationships will be 

 brought out under descriptions of the individual ore bodies, of 

 which some 10 or more have been discovered. In earlier years 

 much attention was directed to them and in at least four instances 

 they have been opened on a scale which has left pits and tunnels 

 of no small size. In one instance, the Split Rock mine, a magnetic 

 mill was built in the hope of reducing the titanium. 



The several deposits will be taken up from north to south so 

 as to begin with the best known and most developed case. 



Split Rock mine. From Westport to the northeast the shores 

 of Lake Champlain are formed by a rugged ridge, known as Split 

 Rock mountain, from the rocky islet which is, as it v\-ere, split off 

 from its extreme point just beyond the limits of our map. Toward 

 Lake Champlain it is precipitous and rough, forming a general fault 

 scarp with many picturesque reentrant bays where cross faults 

 intersect the master one. The summit of the ridge is very irregu- 

 lar but the northwestern slope is more gentle. On the precipitous 

 eastern front and some 5 miles from Westport a mass of titanif- 

 erous ore is exposed at a point about 100 feet above the water. It 

 attracted attention about 40 years ago, and as it stood in a position 

 very convenient for mining and shipping it was opened up on a 

 fairly large scale. Boarding houses were built in a notch in the 

 ridge just above and in the end a mill was erected at the shore of 

 the lake. A road leads out to the westward to the highway as 

 ^hown on the map. 



1 The word ore is here employed in its purely scientitic meaning as 

 implying the richly metalliferous minerals; not in its technical sen>e' as 

 capable of being produced at a profit. 



