The Ore of Charlestown Township

• Age - The Wheatley and Brookdale mines "had pre-cambrian rock formations of great age, called Pickering Gneiss. The Philadelphia Academy of Natural Sciences indicates these rocks are more than 600 million years old."
  
  
• Ore - The dominant material of the veins was quartz, also known to the miners as Gossan. The lead ore for which the mines were worked contained about 30 ounces of silver per ton of ore.
  
  
• The Vein - The Wheatley vein varied in thickness from a few inches to about two and a half feet and its average was thought to be not less than 18 inches. It was bounded by well defined walls the prevailing material of which was a course, soft granite composed chiefly of feldspar (white) and quartz.
  
  
• Yield - In 1865, the NY & Boston Silver Lead Co.'s annual report indicated that in that year (during the "second life" of the Wheatley mine), about 500 pounds of "dressed ore" were mined per 6 foot length of tunnel. In the first three months of 1865, the company shipped 25 tons of ore and had 65 to 70 additional tons on the surface. They also reported they had about 12 tons of "undressed zinc-blend" at that time.
  
  

(Sources)