28 NEW YORK STATE MUSEUM 



ARSENICAL ORE 



The arsenical minerals used for the preparation of arsenical com- 

 pounds include arsenopyrite (iron sulpharsenide), and leucopyrite 

 (iron diarsenide). Both occur in New York State. In addition the 

 hydrous arsenate of iron, scorodite, and the arsenical sulphide 

 orpiment, are known to occur, but are without economic interest. 



An occurrence of arsenopyrite in the Highlands near Pine pond, 

 town of Kent, Putnam county, represents the most important 

 deposit that has actually been developed and exploited for arsenical 

 ore. It was worked in the years 1906-1907 by the Putnam County 

 Mining Corporation which installed a mining and milling plant 

 on the property and shipped a considerable quantity of concentrates 

 as well as several hundred tons of limip ore which was sufficiently 

 high in arsenic to be merchantable. Some of the output went abroad. 

 The deposit was under operation also for a brief time about 1888; 

 a small quantity of ore is reported to have been shipped at that 

 time to New Jersey for treatment. The first exploration seems 

 to date back to 1847. A description of the deposit was given in 

 the issue of the Mining and Quarry Industry for 1906. 



So far as revealed by existing developments, the deposit appears 

 to be a vein intersecting gneiss which is the prevailing formation 

 in this section and includes both igneous and sedimentary varieties. 

 The vein lies near the base of a prominent ridge, southwest of Pine 

 pond. It has a northerly strike. In close proximity and running 

 parallel is a dike of basic rock, the outcropping portion of which is 

 completely altered to serpentine. The dike rises above the surface 

 as a distinct ridge that can be traced for half a mile or more along 

 the strike and shows a width of from 100 to 300 yards. It is probably 

 a peridotite, though the nature of the original silicate minerals can 

 only be inferred from the general appearance and texture, as they 

 are completely altered to serpentine. 



The vein consists of white flinty quartz with varying proportions 

 of arsenopyrite and pyrite. In places the metallic minerals occur 

 in solid mass, but usually they are distributed through the quartz. 

 Pyrite is much the less abundant of the two, its distribution being 

 very irregular. Both are seldom crystallized. The percentage of 

 metallic arsenic in the ore ranges nearly up to the theoretical amount 

 required by the chemical formula. With hand sorting a fairly large 

 proportion will assay above 2 5 per cent which is considered market- 

 able. 



