Aragonite is more commonly found as a constituent of pearl and shell nacre than as a crystal suitable for gem cutting. Too soft for most jewelry use, a faceted aragonite would be a true collector's item.
The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.
|Crystallography||Orthorhombic. Pseudo hexagonal, crystals often acicular, chisel-shaped, prismatic; also massive columnar, fibrous, stalactitic, coralloidal. Frequently twinned.|
|Colors||Colorless, white, yellow, gray, green, blue-green, lavender, reddish, brown.|
|Luster||Vitreous to resinous.|
|Fracture||Fracture subconchoidal. Brittle.|
|Specific Gravity||2.947 (pure). Usually 2.93 – 2.95; up to 3.0 if Pb present.|
|Cleavage||Distinct 1 direction.|
|Luminescence||See "Identifying Characteristics" below.|
|Transparency||Opaque to transparent.|
|Formula||CaCO3 + Pb, Sr, rarely Zn.|
|Optics||α = 1.530; β = 1.681; γ = 1.685. Biaxial (-), 2V = 18°. Sector twinning observed.|
|Etymology||After the locality Molina de Aragon, Spain, where the material was first identified.|
|Occurrence||Worldwide, especially in limestone caverns, hot springs, and in the oxidized zone of ore deposits.|
|Inclusions||Usually veil-type inclusions observed.|
Aragonite and calcite are dimorphous or polymorphs. They share the same chemistry but have different crystal habits. While calcite is the most abundant and widespread carbonate mineral on Earth, aragonite is less so. Facetable aragonites are almost always very small, as opposed to calcites, which occur in huge, transparent masses or crystals.
Be aware that some people describe ammolite as aragonite. However, this mineral only constitutes a part (albeit major) of this fossilized shell gem material.
- Longwave: Pale rose, yellow, tan, green, rarely blueish; also may phosphoresce green (Sicily).
- Shortwave: Yellowish, pinkish-red, tan, and white; also pink (Sicily).
Notable gem sources include:
- Spain: Molina de Aragon, type locality, in stubby twinned crystals.
- Czech Republic: Bilin.
- Greece: Laurium, blue aragonite.
- Sicily: Agrigento, with sulfur crystals.
- Chile: blue material.
- Mexico: Guanajuato.
- United States: Many localities, including Colorado, New Mexico, South Dakota, and Virginia. California, Iowa, and Wyoming yield a fibrous variety.
- Austria; Germany; Namibia; Peru; Slovakia; United Kingdom.
Faceted gems are usually only a few carats and colorless. Potential exists for much larger stones. The largest known cut specimen hails from Bilin. This straw-yellow emerald-cut gem weighs 110 carats.
Straw-yellow crystals from Horschenz, Germany have yielded stones up to 10 carats.
The Devonian Group in Calgary, Alberta, Canada holds a 7.85-ct stone from Germany.
Aragonite’s hardness is too low to allow for safe wear. Avoid mechanical cleaning such as steam or ultrasonic processes. Instead, use a soft brush, mild detergent, and warm water for cleaning. Store your aragonites separately from other stones to avoid contact scratches. Consult our gemstone jewelry cleaning guide for more recommendations.