Belomorite Identification Guide
How to identify belomorite, a peristerite moonstone feldspar with bluish-white sheen, by its adularescence, cleavage, and the clues that separate it from true moonstone.
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What Belomorite Looks Like
Belomorite is a trade/varietal name for a moonstone-like feldspar (a peristerite, an oligoclase-albite plagioclase) from the White Sea (Belomor) region of Russia. It shows a soft schiller. Appearance:
- Color: milky white to grayish, sometimes with peach, yellow, or smoky tints.
- Sheen: a bluish, silvery, or pearly adularescence/schiller that floats across the surface as you tilt it.
- Luster: vitreous to pearly.
- Transparency: translucent to semi-opaque.
- Habit: massive cleavable feldspar; cut as cabochons and beads.
Field-ID Checklist
- Confirm a feldspar look: blocky cleavage planes with flat, reflective surfaces.
- Tilt the stone under a single light and watch for a billowing blue-to-silver sheen that moves.
- Look for the two cleavage directions near 90° characteristic of feldspar.
- Note any fine striations (albite twinning) indicating plagioclase.
- Compare hardness against quartz — feldspar is slightly softer.
Key Diagnostic Tests
- Mohs hardness: 6–6.5; scratches glass, not scratched by a steel knife, scratched by quartz.
- Streak: white.
- Cleavage: two good cleavages intersecting near 90° — diagnostic of feldspar and a key separator from quartz and chalcedony.
- Density: ~2.6–2.65 g/cm³, typical plagioclase.
- Adularescence: the floating internal sheen caused by light scattering on microscopic intergrowths (perthitic/peristeritic lamellae).
- No acid reaction; not magnetic.
Common Look-Alikes and How to Tell Them Apart
- True (orthoclase) moonstone: closely related; both are adularescent feldspars. Belomorite is a peristerite plagioclase from the White Sea, often grayer with a more subdued bluish sheen; precise separation needs feldspar-species testing, and the names overlap commercially.
- Rainbow moonstone (labradorite): shows multicolored flashes (labradorescence) rather than a single soft blue sheen, and is a calcic plagioclase.
- Opalite / glass imitations: man-made; show a uniform milky glow with gas bubbles and no cleavage planes; they fail the cleavage and hardness checks.
- Chalcedony / milky quartz: harder (7), no cleavage, and lacks the moving schiller.
- Selenite (gypsum): much softer (2) and easily scratched by a fingernail.
The combination of feldspar cleavage, hardness ~6, and a soft floating blue-silver sheen identifies belomorite; the locality (White Sea peristerite) defines the variety.
Where It Is Found
Belomorite is named for the White Sea (Belomorye) region of Karelia and the Kola Peninsula, northwestern Russia, where it occurs in pegmatites and metamorphic rocks. Similar peristerite moonstone feldspars are also found in Canada (Ontario, Quebec) and elsewhere, but the "belomorite" name ties to the Russian source.
Frequently asked questions
What is belomorite?
Belomorite is a moonstone-type feldspar (a peristerite plagioclase) from the White Sea region of Russia, showing a soft bluish-silver adularescent sheen. The name comes from Belomorye, the Russian White Sea area.
How can you tell if it's real belomorite?
Real belomorite is a feldspar with two cleavage directions near 90 degrees, a hardness of 6–6.5, a white streak, and a floating blue-to-silver sheen that moves as you tilt it. Glass imitations lack cleavage and show gas bubbles.
Belomorite vs moonstone — what's the difference?
Both are adularescent feldspars. Classic moonstone is usually orthoclase, while belomorite is a peristerite plagioclase from the White Sea, often grayer with a more subdued blue sheen. The names overlap commercially and exact separation needs feldspar testing.
Is belomorite the same as rainbow moonstone?
No. Rainbow moonstone is labradorite that flashes multiple colors (labradorescence), while belomorite shows a single soft bluish-silver sheen (adularescence) and is a peristerite plagioclase.