Orange Calcite with great crystals from Guilin

An orange calcite specimen from Guilin, China, with densely grown scalenohedral crystals whose honey-orange glows with a warm luster. The growth opens up like a chalice, an open structure typical of vug calcite from the karst caves of southern China.

Calcite is calcium carbonate (CaCO₃) and crystallizes trigonally in a variety of forms, from scalenohedra to rhombohedra to dogtooth crystals. With a Mohs hardness of 3, it is one of the softer minerals and reacts sensitively to acid: a drop of vinegar produces the characteristic effervescence, a classic identification method.

The orange coloration is caused by traces of manganese or iron oxides incorporated into the carbonate lattice during crystallization. Such vibrantly colored calcites are considered premium material; most calcite occurrences are colorless to white.

Guilin is located in the karst region of southern China, whose cave system is world-renowned for well-crystallized carbonates. The specimens are recovered under cramped conditions deep within the caves, often several days' trek from the nearest road.

A piece with clear crystallographic structure and the warmest color range that calcite has to offer, suitable for collectors who appreciate the spectrum of carbonate mineralogy.