Orange Calcite

Physical Properties

Hardness: 3 on Mohs scale; Color: Ranges from pale yellow to deep orange; Luster: Vitreous to waxy/resinous; Crystal structure: Trigonal/Rhombohedral; Cleavage: Perfect rhombohedral in three directions; Specific gravity: 2.71

Formation & Geological History

Usually forms through chemical precipitation or in sedimentary environments such as marine settings. It can also be found in hydrothermal veins and as a primary mineral in igneous carbonatites.

Uses & Applications

Used primarily as decorative carvings, tumbled stones, jewelry (though soft), and by collectors. Industrial applications of calcite include cement production, soil treatment, and as a filler in plastics and paints.

Geological Facts

Orange calcite is known for its 'wax-like' appearance when unpolished. It will vigorously effervesce (fizz) when exposed to a drop of cold dilute hydrochloric acid, which is a classic test for calcium carbonate minerals.

Field Identification & Locations

Identify in the field by its softness (can be scratched by a copper penny but not a fingernail), its rhombohedral cleavage, and its reaction to acid. Common locations include Mexico, Brazil, and the USA (notably Utah).

Identified on: 4/18/2026

Mode: Standard