Bytownite Value, Price, and Jewelry Information

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Brilliant shield-cut bytownite, 21.34 cts, 26.7 x 18.1 mm, Mexico. © The Gem Trader. Used with permission.

Although bytownite occurs throughout the world, this feldspar variety is rarely encountered in gem-quality condition.

Bytownite Value

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Bytownite Information

Data Value
Name Bytownite
Is a Variety of Feldspar
Crystallography Triclinic
Refractive Index 1.561-1.570
Colors Colorless, white, gray, yellowish, pale yellow, greenish yellow, greenish, reddish brown.
Luster Vitreous, dull.
Hardness 6-6.5
Fracture Conchoidal to uneven
Specific Gravity 2.72-2.75
Birefringence 0.009
Cleavage Perfect 1 direction, Good 2 directions.
Dispersion 0.012
Transparency Translucent to transparent
Optics α = 1.561; β = 1.565; γ = 1.570. Biaxial (+/-); 2V=86°.
Optic Sign Biaxial +, Biaxial -
Luminescence Present No
Luminescence None
Phenomena May show labradorescence.
Formula (Ca,Na)(Si,Al)4O8
Pleochroism None
Etymology After Bytown (now known as Ottawa), Canada.
Occurrence In basic plutonic rocks, some metamorphic rocks, and meteorites.

Bytownite, 2.5 x 1.9 cm, Dorado Mine, Casas Grandes Municipality, Chihuahua, Mexico. Photo by John Sobolewski. Licensed under CC By 3.0.

What is Bytownite?

Bytownite is part of the plagioclase feldspar solid solution series. It has a composition closer to calcium-rich anorthite than sodium-rich albite, about 70-90% to 10-30%, respectively. Bytownites occur in a great variety of rock types and environments, However, transparent crystals are rare.

Does Bytownite Make a Good Jewelry Stone?

Some plagioclases, like labradorite, make popular gemstones. Nevertheless, with a hardness of 6 to 6.5 and perfect cleavage in one direction and good or imperfect in two others, bytownites are still susceptible to damage from scratches and blows against hard surfaces. As ring stones, bytownites would need protective settings. Use for earrings, pendants, and brooches would be more advisable.

rare gem pendant

This 18K gold brooch/pendant features a 3.31-ct bytownite as the butterfly’s body. Sapphire, boulder opals, Gilson opals, kornerupines, and diamonds comprise other parts. Goldsmith, André Enskat; engraver, H. Postler; gem cutter, H. Lorenz. Photo courtesy of and Henry’s Auktionshaus AG.

Are There Synthetic Bytownites?

There are no known synthetic bytownites or treatments for natural specimens.

Where are Bytownites Found?

Chihuahua, Mexico produces gem-quality bytownites.

In the United States, reddish bytownite pebbles from Arizona and New Mexico have been faceted into small gems. Bytownites have also been reported from Plush, Oregon, a well-known locality for facetable labradorite crystals. Some of these feldspars may have a borderline composition and cross over into the bytownite range.

Other notable gem-quality sources include the following:

  • United States: Minnesota; Montana; Oklahoma; South Dakota; Wisconsin.
  • Japan; South Africa; Sweden; United Kingdom: England, Scotland.
bytownite - Minnesota

Bytownite, Crystal Bay, Minnesota. Photo by Dave Dyet. Public domain.

How to Care for Bytownites

Due to their cleavage, avoid cleaning bytownites with mechanical cleaning systems, like steam and ultrasound. Clean them only with a soft brush, mild detergent, and warm water. Consult our gemstone jewelry cleaning guide for more recommendations.

bytownites - rough and cut set, Mexico

Rough and cut set, bytownites, 3.2 x 2.3 x 1.6 cm (crystal),14.23 ct (cushion step-cut gem), Chihuahua, Mexico. © Rob Lavinsky, Used with permission.

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