Sapphire Gemstone & Information | Gemopedia by JTV | Gemopedia™

Sapphire

September's birthstone has come a long way since the days when any and every blue stone was called a sapphire. Though its fame is shared with its "Big Three" counterparts ruby and emerald, sapphire has enjoyed a long run as one of the world's most beloved gemstones, earning itself a place of honor in crown jewels, royal accessories, museums, and even in modern royal engagement rings. Lest sapphire get too haughty, it has common uses as well. The rough polishing material on emery boards is made up of lower-quality corundum grains, strengthened with hematite, magnetite and quartz.

Colors

Blue, Strongly Greenish Blue, Violet Blue

  • Sapphire classification

    CommonName
    Sapphire
    Species
    Corundum
    Variety
    Sapphire
    Colors
    Blue, Strongly Greenish Blue, Violet Blue
    AlternateNames
    GemstoneGroups
    KeySeparations
    refractive index, birefringence, pleochroism, magnification and spectrum. The observation of natural internal characteristics is a key element in distinguishing natural sapphire from its synthetic counterparts.
    ClassificationComments
  • Sapphire chemistry & crystallography

    ChemicalName
    aluminum oxide
    ChemicalFormula
    Al2O3
    Synthesis
    CrystalSystem
    Trigonal
    ChemistryClassification
    Oxide
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Sapphire optical properties

    Transparency
    Transparent - Opaque
    Dispersion
    Strength: moderate fire Value: 0.018
    OpticalComments
    RefractiveIndex
    1.762-1.77
    Tolerance:(+0.009/-0.005)
    Birefringence
    0.008-0.01
    OpticCharacter
    Uniaxial
    OpticSign
    Negative
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Inert to weak chalky blue or yellowish green
    LWUV: Inert to weak red to orange
    CCFReaction
    Pleochroism
    Dichroic, moderate to strong, varying shades of body color
  • Sapphire characteristic physical properties

    Hardness
    9
    CharacteristicComments
    Streak
    White
    SpecificGravity
    3.95-4.1 Range:0.1/-0.05 Typical:4
    Toughness
    Good
    Inclusions
    Sapphire has type II clarity. Sometimes have silk, rutile, boehmite, apatite, calcite or zircon crystals. Fingerprint and negative crystal inclusions. Hexagonal growth and color zoning. Untreated stones will usually have inclusions intact. Heat treated stones will have fracture halos, discoid fractures or snowballs around crystal inclusions (untreated stones from magmatic areas might also show these characteristics). Silk will be broken and might show sintered areas especially around the girdle.
    Luster
    Bright Vitreous
    Stability
    Very Good
    Fracture
    Conchoidal
    Cleavage
    None