Colemanite Gemstone & Information | Gemopedia by JTV | Gemopedia™

Colemanite

A major source of boron, colemanite was discovered in 1884 and named for the California mine owner where it was first found, William Tell Coleman. The color of this stone ranges from colorless to white to grey, sometimes yellowish. Specimens are very sensitive to heat. The short, prismatic crystals are often sought after by collectors and colemanite is rarely seen in the form of gemstones as it presents a challenge to lapidaries as crystals are soft, brittle and have perfect cleavage.

Colors

Colorless To Grayish White, Yellow

  • Colemanite classification

    CommonName
    Colemanite
    Species
    Colemanite
    Variety
    Colors
    Colorless To Grayish White, Yellow
    AlternateNames
    GemstoneGroups
    KeySeparations
    RI and birefringence
    ClassificationComments
    Colemanite has a high sensitivity to heat.
  • Colemanite chemistry & crystallography

    ChemicalName
    hydrated calcium borate
    ChemicalFormula
    Ca2B6O11.5H2O
    Synthesis
    CrystalSystem
    Monoclinic
    ChemistryClassification
    Borate
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Colemanite optical properties

    Transparency
    Transparent - Translucent
    Dispersion
    Strength: weak fire
    OpticalComments
    RefractiveIndex
    1.586-1.615
    Birefringence
    0.028-0.03
    OpticCharacter
    Biaxial
    OpticSign
    Positive
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV:
    LWUV:
    CCFReaction
    Pleochroism
    None
  • Colemanite characteristic physical properties

    Hardness
    4-4.5
    CharacteristicComments
    Streak
    White
    SpecificGravity
    2.4-2.42
    Toughness
    Poor
    Inclusions
    Luster
    Vitreous
    Stability
    Fracture
    Uneven
    Cleavage
    Perfect, in one direction