Orange Calcite
Calcium carbonate (CaCO3), orange variety of calcite
A soft, glowing orange variety of calcite colored by iron oxides, popular as tumbled stones and known for fizzing in acid.
- Mohs hardness
- 3
- Color
- Pale to bright orange and peach
- Type
- mineral
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Overview
Orange calcite is a colorful variety of calcite, the common calcium carbonate mineral, tinted orange to peach by traces of iron oxide (hematite) inclusions. It is usually massive and translucent rather than well-crystallized.
Calcite is one of the most widespread minerals on earth and a major component of limestone and marble. The orange variety is especially popular in the metaphysical and decorative markets for its warm, glowing color.
Like all calcite, it is soft (hardness 3), has perfect rhombohedral cleavage, and reacts vigorously with dilute acid, fizzing as it releases carbon dioxide. These properties make it easy to identify but also fragile.
Formation & geology
Calcite forms in a vast range of environments. Orange calcite typically precipitates from calcium-rich groundwater in sedimentary and cavity-filling settings, where iron oxide impurities give it the orange color.
It occurs in veins, vugs and cavities within limestone, and as massive deposits associated with hydrothermal and sedimentary processes. Much of the orange calcite on the market comes from Mexico, with other deposits in the United States and elsewhere.
Calcite is also a primary building block of limestone, marble, travertine and many cave formations such as stalactites and stalagmites, forming wherever calcium carbonate is dissolved and re-deposited.
How to identify it
Look for a soft, translucent orange to peach stone with a vitreous to slightly waxy luster. The defining tests are hardness 3 (easily scratched by a steel knife or even a copper coin) and a vigorous fizz when a drop of dilute acid (like vinegar) is applied.
Calcite has perfect cleavage in three directions, breaking into rhombohedral fragments, and clear pieces show strong double refraction (doubling of images). Streak is white.
Look-alikes include orange aragonite (also calcium carbonate but harder and different crystal habit), honey calcite, citrine and orange aventurine. Quartz-based look-alikes are much harder (7) and do not fizz in acid, which is the simplest distinguishing test.
Uses & significance
Orange calcite is mainly sold as tumbled stones, spheres, raw chunks and carvings for decorative and metaphysical use; its softness limits it as a wearable gemstone. Optical-grade clear calcite (Iceland spar) has scientific uses in polarizing optics.
Calcite in general is enormously important industrially as limestone and marble, used in cement, lime, building stone, agriculture and as a flux in metallurgy.
Metaphysically, orange calcite is associated with creativity, energy, motivation and the sacral energy, though these claims are not scientific. Because it is soft and acid-sensitive, it should be kept away from water, acids and abrasion.
Frequently asked questions
What makes orange calcite orange?
Traces of iron oxide such as hematite included within the calcite produce its orange to peach color.
How can I identify calcite?
It is soft (hardness 3), has perfect rhombohedral cleavage, and fizzes vigorously in dilute acid, releasing carbon dioxide.
Is orange calcite the same as citrine?
No. Citrine is quartz (hardness 7, no acid reaction), while orange calcite is calcium carbonate (hardness 3) that fizzes in acid and is much softer.
Can orange calcite get wet?
It is best to avoid water and acids. Calcite is soft and slightly soluble, so prolonged moisture can dull or damage the surface.
Where does orange calcite come from?
Much of the commercial orange calcite comes from Mexico, with calcite deposits occurring worldwide in limestone, veins and cavities.
Orange Calcite guides
In-depth guides for identifying, valuing, and understanding Orange Calcite.
Orange Calcite identified by the community
Real specimens identified with Rock Identifier.
