Rocksday

Franklinite

A black zinc iron oxide almost unique to the famous zinc mines of New Jersey.

Franklinite specimen
Photo: Robert M. Lavinsky, CC BY-SA 3.0, via Wikimedia Commons

How to identify franklinite

  • Black octahedral grains in white calcite.
  • Weakly magnetic.
  • Reddish-brown streak.

Often confused with

Where it's found

  • Franklin and Sterling Hill, New Jersey

Uses

Zinc ore (historically).

Rock tumbling

Not suitable for tumbling.

Did you know?

Franklin, New Jersey, calls itself the Fluorescent Mineral Capital of the World.

Think you could spot it from a blurry close-up?

Play today's Rocksday