Boromuscovite is a rare boron-rich member of the mica group, structurally analogous to muscovite. It typically appears as colorless to pale-colored platy crystals or foliated aggregates, usually found in complex pegmatitic or metamorphic environments where boron enrichment occurs.
Is this boromuscovite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch boromuscovite with a known reference. Boromuscovite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: dull, earthy to porcelaneous.
- 4Match the color rangeCompare against the expected color range: white, beige white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: crystalline, massive.
Often confused with
Boromuscovite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads dull, earthy to porcelaneous on Boromuscovite and vitreous to pearly or silky on Muscovite.
How to tell apart: Luster reads dull, earthy to porcelaneous on Boromuscovite and pearly on Paragonite.
How to tell apart: Luster reads dull, earthy to porcelaneous on Boromuscovite and earthy on Illite.
Often found alongside boromuscovite
Minerals reported to co-occur with boromuscovite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KAl₂(Si₃B)O₁₀(OH)₂
- Mohs hardness
- 2.5-3
- Density
- 2.81 g/cm³
- Colors
- WhiteBeige white
- Streak
- White
- Luster
- Dull, earthy to porcelaneous
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Crystalline, massive
- Cleavage
- Perfect on {001}; poor {010} parting
- Rarity
- Rare
- Uses
- Collector, Scientific research
- Host rock
- A coating on other minerals on the floor of a pegmatite pocket, hydrothermally deposited after rupture of the pocket
Where rockhounds find boromuscovite
Classic worldwide localities
- Little Three mine, Ramona district, San Diego Co., California, USA
Field-hunting tip
Where it forms: A coating on other minerals on the floor of a pegmatite pocket, hydrothermally deposited after rupture of the pocket. If you start seeing lepidolite, quartz, microcline in float, you are in the right ground. Typical habit: crystalline, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify boromuscovite?+
Where is boromuscovite found?+
What rocks look like boromuscovite?+
What minerals are found with boromuscovite?+
What kind of rock does boromuscovite form in?+
What is boromuscovite used for?+
Find boromuscovite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
