Bytownite

Feldspar

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

Bytownite is a rare variety of feldspar named for deposits found in Bytown, Canada (now Ottawa). Some forms of this gem distinctly resemble the gemstone andalusite, another member of the feldspar group.

General Information

Common Name
Bytownite
Species
Feldspar
Transparency
Transparent - Translucent
Dispersion
Strength: Weak Fire Value: 0.012
Refractive Index
1.561-1.583
Birefringence
0.007-0.011
Optic Character
Biaxial
Optic Sign
Negative
Polariscope Reaction
Aggregate (AGG), Doubly Refractive (DR)
Fluorescence
SWUV: Inert
LWUV: Inert
Pleochroism
Unobservable
Hardness
6-6.5
Streak
White
Specific Gravity
2.720-2.740
Toughness
Poor
Inclusions
Bytownite might show labradorescence.
Luster
Vitreous, Dull
Fracture
Conchoidal, Uneven
Cleavage
Perfect, in one direction, Good, in one direction
Chemical Name
calcium sodium aluminum silicate
Chemical Formula
(Ca,Na)(Al,Si)AlSi2O8
Crystal System
Triclinic
Chemistry Classification
Silicate

Bytownite Colors

  • Brown Bytownite
    Brown
  • Gray Bytownite
    Gray
  • White Bytownite
    White
  • Yellow Bytownite
    Yellow

Countries of Origin

Angola; Portugal; Armenia; Greece; Austria; Mongolia; El Salvador; Korea (the Republic of); Morocco; Unknown; Algeria; Argentina; Iran (Islamic Republic of); Hungary; Japan; Ukraine; India; New Zealand; Canada; Belgium; Finland; Italy; South Africa; Antarctica; Ethiopia; Germany; Tanzania, United Republic Of; Russian Federation; Czechia; United States of America; Madagascar; United Kingdom of Great Britain and Northern Ireland; Costa Rica; Saudi Arabia; Sweden; China; Poland; Slovakia; France; Lithuania; Nigeria; Kyrgyzstan; Kenya; Switzerland; Spain; Cuba; Bangladesh; Burkina Faso; Mauritania; Norway; Mexico; Australia; Greenland; Indonesia