MINERALS FROM LYON MOUNTAIN, CLINTON COUNTY 



by' 

 HERBERT P. WHITLOCK 



Early in the spring of 1905 the attention of the writer was di- 

 rected by Mr H. H. Hindshaw, geologist to the Delaware & Hudson 

 Company, to some interesting occurrences of secondary minerals 

 associated with the magnetite deposits of the Chateaugay mines 

 at Lyon Mountain. 



A visit to the mines made in the following summer resulted in 

 the addition to the collection of the New York State Museum of 

 about 150 specimens from this locality. This material augmented 

 by a smaller collection made by Mr D. H. Newland, Assistant 

 State Geologist, and a number of fine specimens presented to the 

 museum as well as some loaned for study by Mr Hindshaw, forms 

 the basis of the following paper. The writer wishes to express his 

 thanks to the above gentlemen as well as to Thomas Cameron, at 

 that time underground foreman, for many valuable suggestions as 

 well as for aid in acquiring material. 



GENERAL DESCRIPTION 



The Chateaugay mines are situated at Lyon Mountain in Clinton 

 county, about 23 miles west of Plattsburg and near the northern 

 boundary of the area of Adirondack gneiss which forms the main 

 outlying mass of the Adirondacks. The workings consist of a series 

 of inclined shafts which in some instances extend to a vertical depth 

 of 800 feet. It was for the most part in the deeper levels of the 

 mine that the openings or "vugs" were encountered which fur- 

 nished the greater mass of the material collected. One of the lar- 

 gest of these now accessible, situated at the 600-foot level, was 

 some 15 feet in length by 3 feet wide and extended vertically to an 

 unknown hight, the bottom being filled with blocks fallen from 

 above. The walls of this cavity, where accessible, were thickly 

 covered with hornblende, apatite, orthoclase and titanite in large 

 and perfect crystals as well as many of the minerals later to be 

 described, in matrix. Most of the calcite specimens of types III, 

 IV and V were obtained from a still larger vug which formerly 



