trigonal Cyclosilicates
Elbaite (Prismatic)
Formula Na(Li,Al)3Al6(BO3)3Si6O18(OH)4
Crystal Structure
#! Species: Elbaite
#! System: Trigonal (3m)
#! Habit: Elongated trigonal prism with striations
trigonal[3m]:{10-10}@1.0[striation:parallel] + {10-11}@0.8 | elongate(c:2.5)
trigonal
3m
{10-10} {10-11}
Quick Facts
Hardness
7.0
Specific Gravity
2.9
Refractive Index
1.615
Optical Character
Uniaxial -
Physical Properties
- Crystal System
- trigonal
- Hardness (Mohs)
- 7.0
- Specific Gravity
- 2.9
- Cleavage
- Indistinct
- Fracture
- Uneven to conchoidal
- Lustre
- Vitreous
Optical Properties
- Refractive Index
- 1.615
- Birefringence
- 0.019
- Optical Character
- Uniaxial -
- Dispersion
- 0.017
- Pleochroism
- strong: Dark tone of body colour / Light tone of body colour (Strong absorption difference; cut with table perpendicular to c-axis for best colour)
- Fluorescence
- Usually inert; weak pink in some rubellite
Characteristics
Colours
Pink (rubellite)Green (verdelite)Blue (indicolite)Colorless (achroite)Watermelon (pink-green)Paraíba (neon blue-green, Cu-bearing)
Localities
Brazil (Minas Gerais, Paraíba)AfghanistanNigeriaMozambiqueMadagascarUSA (California, Maine)
Common Inclusions
Growth tubes parallel to c-axisColour zoningThread-like inclusions
Known Treatments
Heat treatmentIrradiation
Crystal Forms
prismdipyramid
Related Minerals
Other minerals in the trigonal system
