Montebrasite Gemstone & Information | Gemopedia by JTV | Gemopedia™

Montebrasite

Montebrasite is a light green to yellow or colorless gemstone that belongs to the amblygonite group. Similar to amblygonite in chemical composition, it has less fluorine content and twinned crystals are common. Montebrasite was named for its discovery in Montebras, France.

Colors

Colorless, Yellow-Green, Light Green, Light Blue, Pink, Pale Brown, Grayish White

  • Montebrasite classification

    CommonName
    Montebrasite
    Species
    Montebrasite
    Variety
    Colors
    Colorless, Yellow-Green, Light Green, Light Blue, Pink, Pale Brown, Grayish White
    AlternateNames
    GemstoneGroups
    Amblygonite
    KeySeparations
    RI, the lowest RI value of montebrasite 1.594 is lower than RI of 1.612 of amblygonite.
    ClassificationComments
    Often misidentified as amblygonite.
  • Montebrasite chemistry & crystallography

    ChemicalName
    lithium sodium aluminum phosphate
    ChemicalFormula
    LiAl(PO4)(OH,F)
    Synthesis
    CrystalSystem
    Trigonal
    ChemistryClassification
    Phosphate
    Nature
    Natural
    Crystallinity
    Crystalline
    ChemistryComments
  • Montebrasite optical properties

    Transparency
    Transparent
    Dispersion
    OpticalComments
    RefractiveIndex
    1.594-1.633
    Birefringence
    0.02-0.022
    OpticCharacter
    Biaxial
    OpticSign
    Positive
    PolariscopeReaction
    Doubly Refractive (DR)
    Fluorescence
    SWUV: Inert
    LWUV: Inert to weak green
    CCFReaction
    Pleochroism
    Unobservable
  • Montebrasite characteristic physical properties

    Hardness
    5.5-6
    CharacteristicComments
    Streak
    White
    SpecificGravity
    2.98-3.11
    Toughness
    Poor
    Inclusions
    Luster
    Vitreous
    Stability
    Fracture
    Uneven, Subconchoidal
    Cleavage
    Perfect, in one direction, Good, in two directions