Calcite flowers grown on black limestone sugared with small rock crystals

A 100 kg specimen with dense calcite blooms on black limestone, the surface of which is additionally covered by a fine, sugary rock crystal crust. Three mineral generations visible in one piece, born from the South Chinese karst caves of Guilin.

Calcite crystallizes trigonally in various habits, here in the scalenohedral aggregate known as blooms, which consists of densely packed pointed individual crystals. The white to cream-colored hue comes from pure CaCO₃ without Mn/Fe trace elements.

The black limestone matrix underneath is colored by sediment-organic matter, i.e., bituminous material from the original cave floor. The thin layer of rock crystal lying between the matrix and the calcite blooms testifies to a silica-rich solution phase that flushed through between the two carbonate generations.

Such three-layered calcite-rock crystal-limestone specimens are the hallmark of the Guilin region. Extraction takes place underground in karstic cave systems, often days away from the nearest road, which explains the collector's value of large intact specimens.

A textbook example of hydrothermal mineralogy, yet visually impressive enough for a gallery display.