Esperite and Hardystonite


White or dirty white in daylight, esperite exhibits a brilliant yellow fluorescence under SW ultraviolet light, duller yellow under LW ultraviolet. Esperite was also known as calcium larsenite. It occurs with willemite, hardystonite, franklinite and clinohedrite. For many years the only known occurrence was from the Parker Shaft in Franklin, New Jersey. However, microcrystals were recently reported found at El Dragon mine in Potosi', Bolivia.


White, gray-white or tan in daylight, hardystonite exhibits a violet-blue fluorescence under SW ultraviolet light, none under LW. The only known occurrence is at Franklin, New Jersey. Crystals are rare. Hardystonite is almost always accompanied by orange fluorescing clinohedrite.

Rocks from Ken Colosky's Fluorescent Collection

Index of Specimen Images

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