Two varieties of fluorescent sodalite are found in the tinguaite rocks of Magnet Cove, Arkansas: a blue sodalite that fluoresces a purplish-blue to violet-red, and a white variety, hackmanite, which strongly fluoresces a reddish-orange. The hackmanite also exhibits the peculiar phenomenon of evanescence; that is, change of color from rose to colorless and back again with alternate exposures to light and darkness. It shows also the property of photosensitivity; that is, the phenomenon of induced reappearance of the rose color by exposure to ultra-violet radiation and the disappearance of the color in daylight.

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