Calcite

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Named for its calcium content, calcite is one of Earth's more abundant minerals-- you've probably seen it many times and not known exactly what it was. It is found in marble and limestone, as well as other rocks used in industrial settings. Gem-quality calcite, however, takes on a quite different look. You may have seen colorless calcite crystals used as examples for double refraction, but it also forms as white, gray, yellow, pink and green gems. Material is often faceted or polished en cabochon, or carved into ornamental objects.

Calcite Polished
Calcite Classification
Common Name Calcite
Species Calcite
Calcite Optical Properties
Transparency Transparent - Opaque
Dispersion Strength: Moderate Fire Value: 0.170
Refractive Index 1.486-1.658
Birefringence 0.172
Optic Character Uniaxial
Optic Sign Negative
Polariscope Reaction Aggregate (AGG), Doubly Refractive (DR)
Fluorescence SWUV: Variable
LWUV: Variable
Pleochroism None
Calcite Characteristic Physical Properties
Hardness 3
Streak White
Specific Gravity 2.650-2.750 Typical:2.700
Toughness Varies
Inclusions Look for dye concentrations in dyed calcite material.
Luster Vitreous, Greasy
Stability Poor
Fracture Conchoidal, Granular, Splintery
Cleavage Perfect, in three directions
Calcite Chemistry & Crystallography
Chemical Name calcium carbonate
Chemical Formula CaCO3
Crystal System Trigonal
Chemistry Classification Carbonate

Calcite Colors

  • Green Calcite Green
  • Yellow Calcite Yellow
  • White Calcite White
  • Purple Calcite Purple
  • Pink Calcite Pink
  • Orange Calcite Orange
  • Gray Calcite Gray
  • Colorless Calcite Colorless
  • Brown Calcite Brown
  • Blue Calcite Blue
  • Black Calcite Black

Alternate Names

Iceland Spar

Countries of Origin

Tanzania, United Republic Of; Colombia; United States of America (the); Republic of Kosovo; Congo (the); Madagascar; Bolivia (Plurinational State of); India; Spain; Greece; Canada; Pakistan; Unknown; China; Namibia; Russian Federation (the); Brazil; Mexico; South Africa; Australia; Bulgaria; Peru; United Kingdom of Great Britain and Northern Ireland (the)

History

Like so many minerals, calcite is found abundantly throughout the earth. It's found in marble and limestone, and sometimes in the rocks that cover our driveways. Gem-quality calcite is MUCH rarer, and significantly lovelier than its more ordinary family members. It's found in colorless, white, gray, yellow, pink, and green shades. Gem-quality calcite often appears translucent. Because it's so lovely, we are drawn to it as adornment. We recommend you wear and treat calcite with care because it is a 3 on the Mohs scale.

Care

Stones that have low numbers on the Mohs scale are too easily scratched to be very wearable jewelry. That's why a stabilized product is such a great choice. It helps protect the stone, so you can enjoy it for years to come. Do not put calcite - stabilized or natural - in steam or ultrasonic cleaners. Do not expose it to chemicals. Wipe clean with a dry cloth and store away from harder gemstones.

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Species/Variety

Iceland Spar

The colorless, transparent variety of calcite is called "Iceland spar," an important variety for its use in optics, including gemological dichroscopes. Originally discovered in Iceland, gems are most often sold as cleavage pieces that beautifully demonstrate calcite's unique birefringence, or double refraction. Because it is a natural polarizing filter, many believe it was used as a navigational tool by ancient Vikings.

Iceland Spar Calcite
Iceland Spar Classification
Common Name Iceland Spar
Iceland Spar Optical Properties
Birefringence 0.172
Iceland Spar Characteristic Physical properties
Inclusions Iceland spar is identified by strong eye visible doubling and might show adularescence.
Stability Fair
Tim Matthews

Author

Tim Matthews

Tim Matthews is President and Chief Executive Officer of Jewelry Television® (JTV), as well as a member of the company's Board of Directors. He oversees and leads all aspects of the company's powerful omni-digital retail platform that uniquely specializes in fine jewelry and gemstones. His passion for business and gemstones has led him to become a recognized expert in the field of gemology. He is a life member of the Gemmological Association of Great Britain (Gem-A) and has earned Gem-A's highest degrees, the Gemmology (FGA) and Diamond (DGA) diplomas. He is also a Graduate Gemologist (GG) of the Gemological Institute of America (GIA) and has also completed GIA's Graduate Diplomas in Diamonds, Colored Stones and Pearls. Under his leadership, JTV has become the leader in the sourcing and selling of color gemstones and jewelry.

This page was created on June 27, 2014.

This page was last edited on October 24, 2019.