Montebrasite

Montebrasite

By Tim Matthews, JD, FGA, GG, DGA,
CEO and President of JTV (retired)
Published: June 2014
Modified: October 2021
Montebrasite Polished

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.

General Information

Common Name
Montebrasite
Species
Montebrasite
Transparency
Transparent
Dispersion
Strength: None
Refractive Index
1.594-1.646
Birefringence
0.020- 0.030
Optic Character
Biaxial
Optic Sign
Positive or Negative
Polariscope Reaction
Doubly Refractive (DR)
Fluorescence
SWUV: Inert to blue
LWUV: Inert to weak green
Pleochroism
Unobservable
Hardness
5.5-6
Streak
White
Specific Gravity
2.980-3.110
Toughness
Poor
Luster
Vitreous
Fracture
Uneven, Subconchoidal
Cleavage
Perfect, in one direction, Good, in two directions
Chemical Name
lithium sodium aluminum phosphate
Chemical Formula
LiAl(PO4)(OH,F)
Crystal System
Triclinic
Chemistry Classification
Phosphate

Montebrasite Colors

  • Blue Montebrasite
    Blue
  • Brown Montebrasite
    Brown
  • Colorless Montebrasite
    Colorless
  • Gray Montebrasite
    Gray
  • Green Montebrasite
    Green
  • Pink Montebrasite
    Pink
  • White Montebrasite
    White
  • Yellow Montebrasite
    Yellow

Countries of Origin

Myanmar; Unknown; Brazil

Care

Normal care