Calcium-rich plagioclase feldspar. Rare as a gem but important petrologically in mafic igneous rocks. Color: White to dark gray. Luster: Vitreous. Streak: White. Cleavage: Perfect in two directions. Hardness: 6-6.5. Transparency: Translucent to opaque. Crystal system: Triclinic. Chemical formula: Ca,Na Al,Si AlSi₂O₈. Specific gravity: 2.72-2.74. Formation: Crystallizes from calcium-rich mafic magmas in gabbros and norites. Common geological settings: Bytown Ottawa , Canada; found in gabbro, norite, and anorthosite. Common look-alikes and related entries: Labradorite, Anorthite, Andesine.
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These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.
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Last updated
2026-03-30T14:36:44.886096+00:00
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IMA–CNMNC List of Mineral Names — International Mineralogical Association. Official mineral-name, nomenclature, and classification records.
Mineral ID Key — Mineralogical Society of America. Physical-property identification methods, repeat-testing guidance, and limitations.
Calcium-rich plagioclase feldspar. Rare as a gem but important petrologically in mafic igneous rocks.
How can you identify Bytownite?
Compare several properties rather than relying on colour alone. This entry records colour: White to dark gray; lustre: Vitreous; streak: White; Mohs hardness: 6-6.5; cleavage: Perfect in two directions; crystal system: Triclinic; transparency: Translucent to opaque. Confirm an important identification with additional field tests or qualified laboratory work.
How does Bytownite form?
Crystallizes from calcium-rich mafic magmas in gabbros and norites.
Where is Bytownite commonly found?
Bytown Ottawa , Canada; found in gabbro, norite, and anorthosite.
What is Bytownite commonly confused with?
Bytownite may be confused with Labradorite, Anorthite, Andesine. Compare multiple diagnostic properties because colour and surface appearance can overlap.
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