Calcite and Galena on Calcite (Cast) - image 1

Calcite and Galena on Calcite (Cast) - image 2

Calcite and Galena on Calcite (Cast)

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This is a really neat specimen that shows multiple stages of growth and replacement as the chemistry in the pocket changed over geological time. First of all, it is pretty on its own merits, with the sparkly galenas perching on contrasting calcite. The whole matrix is a cast after a previous large calcite rhombohedron: and it is this cast of rhombohedral calcite that is festooned with galena, to 5 mm across. Under the calcite cast and separated from it is a well formed rhombohedron of lustrous and slightly translucent, ivory-colored calcite, measuring 3.75 cm across.This rhombohedron fluoresces a mild orange color (due to trace manganese content). The rhomb would have formed at a later date, after the original calcite was hollowed out and eaten away by fluids in the pocket. I find it startling to see a perfect, sharp later-generation rhombohedra, within the cast of the original crystal, of the same species! It is like a little clone growing inside, and the even spacing and symmetry give the piece a striking display angle and a fascinating story.