Orange-colored coral-like calcite with two generations of crystals grown on top of each other

An orange-colored coral-like calcite from Guilin, China, in which two generations of crystals have grown on top of each other. The growth habit is reminiscent of branched coral structures, a dense aggregate of smaller scalenohedra.

Calcite (CaCO₃) crystallizes in more habit varieties than almost any other mineral. The coral-like structure results from radially-radiating growth from central growth nuclei, which send out branched micro-scalenohedra in all directions.

The two generations are recognizable as layers: a first phase with finer microcrystals, then a second with coarser scalenohedra that overgrew the first layer. A visible stratigraphy of two carbonate solution phases.

The orange coloration comes from manganese and iron traces during crystallization. Guilin provides strongly colored calcites of collector quality; the South Chinese karst deposit is a premium source for carbonate minerals.

A collector's item with educational two-generation mineralization and unusual growth geometry.