History · Geology
About Franklin and Sterling Hill
Franklin and the neighboring Sterling Hill (Ogdensburg) deposits in northern New Jersey are the world’s most species-diverse and most fluorescent-mineral-prolific localities. Together they have yielded over 350 mineral species, of which more than 90 fluoresce vividly under UV light.
Geology
The deposits are stratiform Zn-Fe-Mn ore bodies in metamorphosed Mesoproterozoic Franklin Marble. Granulite-facies metamorphism produced an unusual Zn-Mn-Fe oxide-silicate-borate paragenesis found at essentially no other locality on Earth.
Notable Minerals
Willemite (the green fluorescent star), franklinite (black spinel, locality’s namesake), zincite (red), hardystonite (UV-fluorescent purple), calcite (red UV fluorescence), rhodonite, tephroite, andradite (Mn-rich), bustamite, and dozens of unique Mn-Zn species.
Collector Notes
Franklin specimens combining willemite (green UV), zincite (red), franklinite (black non-fluorescent), and calcite (red UV) are the iconic American fluorescent-mineral display. Mining at Franklin ceased in 1954, Sterling Hill in 1986; supply is finite.
Minerals Produced Here
- Andradite (钙铁榴石)
- Calcite (方解石)
- Franklinite (锌铁尖晶石)
- Gahnite (锌尖晶石)
- Hardystonite (硅锌钙石)
- Rhodonite (蔷薇辉石)
- Willemite (硅锌矿)
- Zincite (红锌矿)
