Bytownite Value, Price, and Jewelry Information

Bytownite By Dave Dyet (Own work) [Public domain], via Wikimedia Commons

Bytownite

Bytownite Value

The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.

Bytownite Value via Gem Price Guide

Accompanying value information:
Faceted 1 to 3 carats
TO /ct

Bytownite Information

Data Value
Name Bytownite
Is a Variety of Feldspar
Colors Yellowish, reddish brown
Crystallography Triclinic.
Refractive Index 1.561-1.570
Luster Vitreous, dull
Hardness 6 - 6.5
Fracture Conchoidal to uneven
Specific Gravity 2.72-2.75
Birefringence 0.009
Cleavage Perfect
Dispersion 0.012
Transparency Translucent to transparent.
Optics

α = 1.561; β = 1.565; γ = 1.570. Biaxial (-); 2V=86°.

Optic Sign Biaxial -

Comments

These feldspars are rarely encountered in gem form. Their occurrence is widespread throughout the world, in a great variety of rock types and environments, but in most cases transparent crystals are rare.

In many cases faceted gems are identified as a feldspar in the plagioclase series, but the finder does not have the instrumentation needed to pin down the species. This is accomplished by a combination of optical and X-ray analysis. A few plagioclase gems have been well characterized, however, and reported in the literature.

Name

Bytown, Canada, gave its name to bytownite.

Occurrence

Bytownite is found in basic plutonic rocks, some metamorphic rocks, and meteorites. Localities include Montana; South Dakota; Oklahoma; Minnesota; Wisconsin; Scotland; England; Sweden; Japan; and South Africa. Bytownite is sometimes reddish in color and pebbles from Arizona and New Mexico have been faceted into small gems. Bytownite is also reported from Plush, Oregon, but this is a well-known locality for labradorite in facetable crystals; it may be that some of the feldspar has a borderline composition and crosses over into the bytownite range.