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Webster 1913 Edition

Noun.

[Named after

Karl

Giesecke

(Min.)

A mineral occurring in greenish gray six-sided prisms, having a greasy luster. It is probably a pseudomorph after elæolite.

Noun.

A mineral of a rhomboidal form and compact texture, of a gray or brown color, and nearly as hard as calcarious spar.

gieseckite ‎(uncountable)