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Two contenders for the title of 'State Mineral of New Jersey'

New Jersey has an official state animal, a state flower, even a state dance, but it does not have an official state mineral. In order to become "official", the state Legislature has to adopt the item and sign documentation to acknowledge such recognition. For many years now, geologists and non-professional "Rock Hounds" around the state have argued over which mineral should be considered the "state mineral".

"Ladies and gentleman, let the battle begin....."

Franklinite In this corner, with a chemical formula of (Zn, Mn2+,Fe2+)(Fe3+,Mn3+)2O4, a specific gravity of 5.0-5.2, and a hardness of 6, New Jerseys' own Franklinite.

Discovered in, and named after, the town of Franklin, New Jersey, Franklinite, is found in great abundance in the northwest part of the state, but is very rare in other parts of the world.

Franklinite, which contains zinc, iron, and manganese was mined in great quantity from colonial times up till the early 20th century.

Franklinite is dark black, has a reddish brown streak and a metallic luster. It is found in massive, granular and, occasionally, in crystallized forms. The crystal system is cubic (isometric) and the mineral is slightly magnetic. Specimens are still collected at Franklin and Sterling Hill.

Prehnite And in the opposite corner, with a chemical formula of Ca2Al(AlSi3O10)(OH)2, a specific gravity of 2.9+, and a hardness of 6-6.5, the beautiful and much sought after mineral Prehnite.

First discovered at the Cape of Good Hope, South Africa, by Colonel Hendrik Von Prehn. Colonel Prehn became the first person to ever have a mineral named after him.

Prehnite contains calcium and aluminium and forms as a result of low grade metamorphism usually from hydrothermal solutions. The crystals are often found as thick crusts within cavities of igneous rocks.

Prehnite is usually a translucent light green, but can be grey, white or colorless. The streak is white, and the luster is vitreous to waxy or pearly. The orthorhombic crystals are brittle and fracture unevenly. Prehnite is found in many locations around the world, with notable occurrences in Connecticut, Pennsylvania, Virginia, and Patterson, New Jersey.

New Jersey also has an official state dinosaur; Hadrosaurus foullki, the fossil skeleton that was discovered in Haddonfield in 1858. To learn more about the official state symbols, click HERE.

To read about the unofficial state rock, click HERE.

New Jersey Geological Survey Logo Additional Information
New Jersey Geological Survey
NJDEP, PO Box 427
Trenton NJ 08625
Phone: 609-292-2576
Fax: 609-633-1004