ADIRONDACK MAGNETIC IRON ORES 1 47 



in Essex and southern Franklin counties and consists of a connected 

 mass which spreads over a surface of some 1 200 square miles. There 

 are smaller outlying intrusions in Clinton and Warren counties and 

 in the western Adirondack region. The greater number of deposits 

 are found within the bordering portions of the main anorthosite 

 area in the townships of Westport, Elizabethtown and Newcomb, 

 Essex co. In the central part no large bodies are known. A 

 deposit near Port Leyden, Lewis co., is the only occurrence outside 

 of the main area that has been the object of exploitation. 



General geological relations and origin of the deposits 



The titaniferous deposits constitute a well marked type of ore 

 occurrence that is quite widely distributed in this and foreign 

 countries. They are known to be of considerable extent in Minne- 

 sota, Wyoming and Colorado, in the Provinces of Ontario and 

 Quebec, and in Sweden, Norway and Brazil. The Taberg deposit 

 in Sweden was mined for a number of years and the ore used for the 

 manufacture of. iron. The various localities for titaniferous 

 magnetites have been described briefly in a paper by Professor 

 Kemp. 1 The occurrences throughout show a remarkable degree 

 of uniformity in the essential features of their geological surround- 

 ings and composition of the ores. 



With a single exception the country rocks of the Adirondack 

 deposits, as is generally the case elsewhere, are members of the 

 gabbro family. The prevailing rock in the Adirondack region 

 is the variety known as anorthosite, the predominant constituent 

 of which is a basic plagioclase feldspar, usually labradorite. The 

 rock is the first of a series of related intrusions in the region that 

 were derived apparently from a common magma. Gabbro in 

 the restricted sense, syenite and probably granite are represented 

 among the later intrusions derived from the same source. Most 

 of the deposits are found within dikes and masses of gabbro which 

 occur at intervals throughout the anorthosite area. Some of the 

 large bodies at Lake Sanford, however, are inclosed directly by 

 the anorthosite. 



The general characters of the gabbros and anorthosites have 

 already been set forth in the part of this report relating to Adiron 

 dack geology. The following analyses taken from Professor 

 Kemp's paper give details as to the chemical composition of t) T p- 



*A Brief Review of the Titaniferous Magnetites. Columbia Univ. Sch. of 

 Mines Quarterly, July 1899. 



