Gypsum

This impressive specimen, no. MB160 in the collection of Mark Boyer, boasts several “eyes” of fine-grained white roeblingite (largest in upper left quadrant) with massive brown andradite, black franklinite, and lustrous brown plates of hendricksite in a matrix of mixed, hydrothermally altered minerals of dominantly white color. One of these white minerals, present in abundance, is dull-lustered, fluoresces blue SW, and upon sale to Mr. Boyer had been optimistically regarded as xonotlite. Instead it is gypsum; see photo GYP11b.

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