Bytownite is a calcium-rich member of the plagioclase feldspar group, representing the compositional range between labradorite and anorthite. Collectors identify it by its specific gravity and optical properties often associated with mafic intrusive rocks like gabbros.

Hardness

6-6.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineraluncommonPlagioclase Feldspar Series family

Bytownite

Hardness: 6-6.5
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this bytownite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch bytownite with a known reference. Bytownite sits at Mohs 6-6.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Bytownite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Bytownite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, gray, yellowish, colorless.
5
Look at form & habit
Crystal system: triclinic. Typical habit: tabular crystals, massive, granular.

Often confused with

Bytownite vs. its common look-alikes — and how to tell them apart in the field.

Often found alongside bytownite

Minerals reported to co-occur with bytownite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: (Na,Ca)(Al,Si)₄O₈
Mohs hardness: 6-6.5
Density: 2.72-2.75 g/cm³
Colors: White Gray Yellowish Colorless
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Triclinic
Crystal habit: Tabular Crystals, Massive, Granular
Cleavage: Perfect in Two Directions At Nearly 90 Degrees
Rarity: Uncommon
Uses: Collector, Scientific Research
Host rock: Mafic Igneous Rocks Such as Gabbro and Anorthosite
Typical price: $10-50 for small specimens

Where rockhounds find bytownite

Classic worldwide localities

Ontario, Canada
Norway
Scotland
Japan
South Africa

Field-hunting tip

Look in mafic igneous rocks such as gabbro and anorthosite country — that is the host setting where bytownite typically forms. If you start seeing pyroxene, amphibole, olivine in float, you are in the right ground. Field specimens usually show a tabular crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify bytownite?+

Mohs hardness is 6-6.5. It typically shows a vitreous luster. The streak is white. Common colors include white, gray, yellowish, colorless.

Where is bytownite found?+

Notable localities include Ontario, Canada; Norway; Scotland; Japan; South Africa.

How much is bytownite worth?+

Typical asking prices fall in the range of $10-50 for small specimens. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like bytownite?+

Bytownite is most often confused with Labradorite, Anorthite, Albite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with bytownite?+

Bytownite commonly co-occurs with Pyroxene, Amphibole, Olivine, Magnetite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does bytownite form in?+

Bytownite typically forms in mafic igneous rocks such as gabbro and anorthosite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is bytownite used for?+

Bytownite is used in collector, scientific research.

Find bytownite on the map

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