Calcite | Gemopedia

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 granite and limestone veins and streaks as well as other rocks used in driveways and roads. Gem-quality calcite, however, takes on a quite different look. You may have seen colorless calcite crystals used as examples for double image 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.
Alternate
Names
Limespar
Colors
White, Yellowish, Pink, Orange, Colorless, Any Color If Dyed

Calcite Classification

Common Name

Calcite

Species

Calcite

Variety

Colors

White, Yellowish, Pink, Orange, Colorless, Any Color If Dyed

Alternate Names

Limespar

Gemstone Groups

Calcite

Key Separations

RI, birefringence, SG, eye visible doubling, cleavage and appearance. Use birefringence blink method.

Comments

Might be thermoluminescent phosphoresce upon heating or triboluminescent luminescence caused by friction.

Calcite Optical Properties

Transparency

Transparent - Opaque

Refractive Index

1.486-1.658

Birefringence

0.172

Optic Character

Uniaxial

Optic Sign

Negative

Polariscope Reaction

Doubly Refractive (DR)

Fluorescence

SWUV: Variable
LWUV: Variable

CCF Reaction

Pleochroism

None

Dispersion

Strength: moderate fire Value: 0.17

Comments

Calcite Chemistry & Crystallography

Chemical Name

calcium carbonate

Chemical Formula

CaCO3

Synthesis

Crystal System

Trigonal

Classification

Carbonate

Nature

Natural

Crystallinity

Crystalline to Aggregate

Comments

Calcite Characteristic Physical Properties

Hardness

3

Streak

White

Specific Gravity

2.65-2.75 Typical:2.7

Toughness

Varies

Inclusions

Look for dye concentrations in dyed calcite material.

Luster

Vitreous

Stability

Poor

Fracture

Conchoidal, Granular, Splintery

Cleavage

Perfect, in three directions

Comments

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