monoclinic Simulant turquoise simulant
Dyed Howlite (Turquoise Simulant) (Dyed Howlite (Blue))
Formula Ca2B5SiO9(OH)5 (calcium borosilicate hydroxide; dyed blue to simulate turquoise)
Crystal Structure
#! Species: Dyed Howlite (Ca2B5SiO9(OH)5; turquoise simulant)
#! System: Monoclinic (2/m)
#! Habit: Massive; porous; dye concentrates at fractures
monoclinic[2/m]:{010}@1.0 + {110}@0.5 + {001}@0.7
monoclinic
2/m
{010} {110} {001}
Quick Facts
Hardness
3.0
Specific Gravity
2.53
Refractive Index
1.583
Optical Character
Biaxial -
Physical Properties
- Crystal System
- monoclinic
- Hardness (Mohs)
- 3.0
- Specific Gravity
- 2.53
- Cleavage
- None (but howlite is porous)
- Fracture
- Conchoidal
- Lustre
- Sub-vitreous to waxy
Optical Properties
- Refractive Index
- 1.583
- Birefringence
- 0.022
- Optical Character
- Biaxial -
- Fluorescence
- Variable
Origin & Identification
- Origin
- Simulant
- First Produced
- 1960
- Diagnostic Features
- Dye bleeding at fractures and vugs under 10x loupe; hardness 3-3.5 (scratched by copper coin vs turquoise H 5-6); acetone swab removes blue dye; FTIR borosilicate spectrum vs turquoise phosphate; Chelsea filter reaction differs from natural turquoise; birefringence 0.022 measurable
Characteristics
Colours
Blue to blue-green (dyed); also sold undyed as white howlite
Common Inclusions
Dye bleeding at fractures and vugs (diagnostic under loupe)
Notes
Howlite (Ca2B5SiO9(OH)5) is a natural calcium borosilicate hydroxide mineral; monoclinic 2/m. When dyed blue it closely resembles turquoise. The dye is the simulant aspect. Webster 1962, Journal of Gemmology 8(8):286 (DOI 10.15506/jog.1962.8.8.286) [VERIFIED]: "A New Turquoise Simulant" — first documented dyed howlite as turquoise simulant. Key diagnostics: (1) dye bleeding at fractures/vugs (visible under 10x loupe — natural turquoise shows even colour); (2) hardness 3-3.5 (scratched by copper coin; turquoise H 5-6); (3) acetone swab removes blue dye (natural turquoise colour is intrinsic); (4) FTIR shows borosilicate spectrum (vs phosphate spectrum of turquoise); (5) birefringence 0.022 on flat face (turquoise birefringence too small to observe). Also marketed as "white buffalo turquoise" (undyed) or simply "turquoise" (when dyed). Primarily from California, USA and Canada.
Related Minerals
Other minerals in the monoclinic system
