Chalcopyrite, a copper iron sulfide mineral, is known from both Franklin (Palache, 1908, 1935) and Sterling Hill (Farrington, 1851). It has been little studied and is not a mineral of economic significance locally.
Chalcocite is dark gray-black, commonly oxidized (sooty) on exposure, and sectile. It is sometimes confused with djurleite, from which it is best differentiated using X-ray methods. Secondary malachite, azurite, and brochantite are common alteration products.
Chalcocite from Franklin occurs in seams in the ore, commonly associated with magnetite or franklinite; quartz is common to some assemblages. The most noteworthy occurrence is as the matrix for fine magnetite crystals and native silver.
Chalcocite is known from several assemblages at Sterling Hill, in particular with rhodonite on the 700 level and with franklinite and calcite from the north orebody. An occurrence below the 700 level was noted by Jenkins and Misiur (1994). Small amounts are found in the common sulfide veins, in atypical assemblages not noted here, and in many one-of-a-kind specimens. (Dunn, 1995)

 Location Found: Franklin and Ogdensburg
 Formula: Cu2S
 Essential Elements: Copper, Sulfur
 All Elements in Formula: Copper, Sulfur
 IMA Status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
 To find out more about this mineral at minDat's website, follow this link   Chalcocite

Dunn, Pete J. (1995). Franklin and Sterling Hill New Jersey: the world's most magnificent mineral deposits. Franklin, NJ.: The Franklin-Ogdensburg Mineralogical Society. p.531

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.49

The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 35, No. 2 - Fall 1994, pg. 21A Complex Base-Metal Assemblage From the Sterling Mine New Jersey - Chalcocite/Digenite/Covellite
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