Bytownite Gemstone: Properties, Meanings, Value & More

Bytownite is a feldspar variety that’s commonly colorless to yellow. The mineral’s name comes from its discovery in Bytown, the former name for Ottawa, Canada.

Is bytownite rare? As a mineral, bytownite is fairly abundant; it’s found all over the world and even in meteorites. However, it’s still the rarest plagioclase feldspar and bytownite gemstones are rare.

That said, some sunstones and “rainbow moonstones” (a labradorite variety) have been found to have bytownite composition.

Intrigued? Come along to learn bytownite’s properties, prices, powers, history, and more!

Image credit: DonGuennie, CC-BY-SA-4.0

About Bytownite Stone

Bytownite is a rare semi-precious gemstone that’s commonly colorless or pale yellow. It’s sometimes called “calcic plagioclase,” but this term has been used for all calcium-dominant plagioclase feldspars — bytownite, anorthite, and labradorite — and today “anorthite” is a more accurate term for these.

Like labradorite, some bytownites can display the iridescent color flashes called “labradorescence.”

Some bytownites resemble andalusite, an aluminosilicate mineral that’s much more common as gemstones, with a higher density and strong pleochroism (which bytownite lacks).

Astrologically, bytownite is a Capricorn birthstone.

Industrially, what is bytownite used for?

Bytownite Uses

Feldspars are important industrially, though alkali (potassium) feldspars are used more than plagioclase feldspars. The top feldspar uses are in the ceramic and glass industries, but calcium-rich plagioclase feldspars like bytownite and anorthite are primarily used in construction like strengthening glass-reinforced plastic or making fiberglass.

More recently, however, calcium-rich plagioclases have been used for:

• Paint, rubber, and plastic fillers or extenders

• Archeological dating elements

• Dental porcelains

In 1996, researchers successfully produced especially pure silicon (99.79 to 99.98 pure) by using a molten mixture of bytownite and cryolite mixture to electrotwin the substance.

In 2000, a bulletin on anorthosites (rocks composed of only plagioclase feldspars) in Norway reported that local bytownite-anorthosites was industrially valuable as an alternative to imported bauxite for sourcing aluminum.

In 2021, scientists published a review of engineered (synthetic) feldspar-based ceramics and their various beneficial properties. In the review, they studied using industrial waste glasses as precursors for making glass-ceramics of bytownite and labradorite.

Bytownite Specifications & Characteristics

The main feldspar groups are alkali (aka potassium feldspar or K-feldspar) and plagioclase.

Plagioclase feldspars have compositions between albite (sodium-dominant; NaAlSi3O8) and anorthite (calcium-dominant; CaAl2Si2O8). The plagioclase series goes from albite to anorthite, with each mineral in the series having increasing anorthite content.

Bytownite is just above anorthite in the plagioclase series, with 70 to 90 percent anorthite and 10 to 30 percent albite. The bytownite formula can be written as (Ca,Na)(Si,Al)4O8 or (Ca,Na)[Al(Al,Si)Si2O8]. The mineral is a calcium sodium aluminum silicate.

Some mineralogists classify bytownite as a variety of anorthite.

Other plagioclase feldspars are andesine, oligoclase, and labradorite. Labradorite is just above bytownite with 50 to 70 percent anorthite and 30 to 50 percent albite.

Distinct bytownite crystals are rare but they’re usually tabular, finely striated, and twinned. They can show albite, Carlsbad, or Pericline twinning.

More often, bytownite occurs as cleavable masses, small, faceless grains in aggregates, blocky crystal fragments, or compact crystal clusters.

You need X-ray diffraction, petrographic analysis, or chemical analysis to find the precise density (specific gravity) and refractive indices to identify a bytownite definitively.

Bytownite properties listed:

• Mohs hardness: 6-6.5

• Color: Colorless, white, gray, yellow, greenish-yellow, pale green, reddish-brown

• Crystal structure: Triclinic

• Luster: Vitreous or dull, pearly on cleavages

• Transparency: Translucent, rarely transparent

• Refractive index: 1.561-1.583

• Density: 2.72-2.75

• Cleavage: Perfect on [001], Good/distinct on [010] & [110]

• Fracture: Conchoidal or uneven/irregular

• Streak: White

• Luminescence: None

• Pleochroism: None

• Birefringence: 0.007-0.011

• Dispersion: 0.012 (weak)

• Optical phenomena: Sometimes labradorescence, rarely aventurescence

Image credit: John Sobolewski, CC-BY-SA-3.0

Bytownite History

Dr. Andrew Fernando Holmes — a Spanish-Canadian physician, chemist, botanist, and mineralogist — first discovered bytownite near Bytown (now Ottawa) in Canada.

He submitted the greenish-white specimen to his colleague, Scottish chemist and mineralogist Dr. Thomas Thomson, who published the first description of the stone in 1836. In his description, Thomson named the stone “bytownite” after the neighborhood where Holmes found it.

Thomson is also known for giving the element silicon its name in 1817 and discovered the zeolite mineral thomsonite in 1820, which was named after him.

Austrian mineralogist Gustav Tschermak, who first submitted the theory that plagioclase feldspars were mixtures of albite and anorthite in 1864, used “bytownite” for any feldspar with a composition between labradorite and anorthite.

However, in 1863, American geologist and chemist Thomas Sterry Hunt published his analysis of the original material as “bytownite-anorthosite,” an anorthosite variety. This analysis was in the significant, 983-page Geological Survey of Canada: Report of Progress from its Commencement to 1863.

In 1893, German geologist Ferdinand Zirkel confirmed that the original material was actually a mixture.

In 1915, the Geological Survey of Canada’s Memoir 57 published an official update on the original bytownite material being a mixture containing bytownite, anorthosite, spinel, and chondrodite.

Unfortunately, the original locality of bytownite can’t be found anymore, and the original specimens are very hard to find, even in collections.

Bytownite Healing Properties

As an often yellow healing stone, bytownite’s meaning reflects that of other yellow gemstones in promoting creativity, joy, and success. Bytownite crystals also function as solar plexus chakra stones.

Physical Healing

Physically, bytownite’s metaphysical properties are said to help with issues related to:

• Skin

• Stomach

• Spleen

• Kidneys

• Metabolism

Emotional Healing

Emotionally, bytownite is believed to help you harness but also control your strength, boosting confidence and self-assurance while providing wisdom and mental clarity so you don’t lash out or explode, so to speak.

Crystal healers recommend bytownite for strengthening relationships, as it’s said to bring a fresh spark and closer intimacy to all partners.

Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Bytownite Gemstone Properties

Besides their rarity, bytownite gemstones are valued based on color, cut, clarity, transparency, and carat weight.

Color

What color is bytownite? While the mineral is usually colorless, white, or gray, gemstones are often more colorful with shades of yellow, greenish-yellow, or reddish-brown.

Some rare Oregon sunstones (types of sunstones with aventurescence from copper inclusions instead of hematite or goethite) from Ethiopia were found to have compositions at the labradorite-bytownite boundary.

Research by the Gemological Institute of America (GIA) in 2009 showed that heat treatments turned some Oregon labradorites into bytownite.

Additionally, the trade name “rainbow moonstone” used to apply to colorless bytownites from India that had labradorescence and lacked the typical dark ilmenite inclusions seen in labradorite from other sources.

Cut

Since gem-quality bytownite specimens are rare, so are faceted bytownites, making them more valuable.

Bytownites with good transparency, maybe in the sunstone or rainbow moonstone variety, often become cabochons. Most bytownite specimens are sold rough (uncut).

Clarity & Transparency

Clarity describes the degree of visible inclusions in a stone, which can negatively affect its transparency and value. Fewer inclusions and higher transparency (which is rare in bytownite) make the stone more valuable.

A faceted bytownite, however, may still be valuable even with inclusions. Potential inclusions include feather-like liquid and glass.

Bytownite has also been found as an inclusion in Moroccan agate and Montana sapphire stones.

Carat Weight & Size

Bytownite crystals and specimens can be large, but faceted gems over 10 carats are rare.

Image credit: Dave Dyet, Public domain

Bytownite Formation & Sources

Bytownite minerals form in a variety of rocks, including stony meteorites.

Most often, it’s found in igneous rocks, particularly plutonic ones like bytownite olivine-gabbro and bytownite-troctolite or volcanic ones like manganese-rich basalt. These rocks often contain olivine and pyroxene as well.

The mineral is less often found in metamorphic rocks.

Geographically, where is bytownite found?

Mining Locations

Bytownite specimens are abundant, but gem-quality specimens are less so. The best gem-quality bytownites come from Mexico and Oregon (USA). Arizona and New Mexico, USA, have also produced facetable crystals.

Other significant sources for attractive bytownites include:

• Australia

• Canada

• Japan

• Norway

• South Africa

• Sri Lanka

• Sweden

• USA (Minnesota, Montana, Oklahoma, South Dakota, Wisconsin)

• UK (England, Scotland)

Image credit: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0

Bytownite Price & Value

First, let’s look at faceted gems.

Bytownite’s price per carat when faceted generally ranges from around $20 to $40 per carat, or about $50 to $300 each, though particularly large ones can be over $1,300 each.

Rough specimens are much lower, starting around $0.25 per carat. Strands of bytownite beads are around $0.80 to $2 per carat or around $170 to $220 per strand.

Tumbled stones are about $5 each. Translucent or “sunstone” bytownite cabochons are generally around $20 to $40.

Bytownite Care and Maintenance

For gemstone care, bytownite is relatively hard but has perfect cleavage, so any jewelry (particularly rings) should have protective settings.

Only clean bytownites with mild soap, warm water, and a soft toothbrush. Avoid mechanical cleaning systems.

Brighten Your Life with Bytownite!

Bytownite is a lesser-known feldspar, but its charming yellow color is full of joy. Although faceted bytownites may be rarer than other feldspars, there are plenty of rough specimens at affordable prices to bring this crystal’s brightness into your life.

Buy bytownite gemstones today!