Cappelenite-(Y) is a very rare silicate-borate mineral primarily found in alkaline pegmatites. It typically occurs as small, hexagonal prismatic crystals that are often heavily etched or poorly defined, appearing in shades of brown to greenish-brown.
Is this cappelenite-(y)?
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 cappelenite-(y) with a known reference. Cappelenite-(Y) sits at Mohs 6-6.5, 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: vitreous to greasy.
- 4Match the color rangeCompare against the expected color range: greenish brown.
- 5Look at form & habitCrystal system: trigonal. Typical habit: prismatic.
Often confused with
Cappelenite-(Y) vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Cappelenite-(Y) leaves white, Gadolinite-(Y) leaves greenish gray.
How to tell apart: Streak differs, so Cappelenite-(Y) leaves white, Allanite leaves gray; luster reads vitreous to greasy on Cappelenite-(Y) and submetallic on Allanite.
Often found alongside cappelenite-(y)
Minerals reported to co-occur with cappelenite-(y). Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- BaY₆B₆Si₃O₂₄F₂
- Mohs hardness
- 6-6.5
- Density
- 4.407 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous to greasy
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Prismatic
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a small vein in nepheline syenite pegmatite
Where rockhounds find cappelenite-(y)
Classic worldwide localities
- Lille Arø Island, in the Langesundsfjord, Norway
Field-hunting tip
Where it forms: In a small vein in nepheline syenite pegmatite. If you start seeing wöhlerite, rosenbuschite, thorite in float, you are in the right ground. Typical habit: prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cappelenite-(y)?+
Where is cappelenite-(y) found?+
Is cappelenite-(y) safe to handle?+
What rocks look like cappelenite-(y)?+
What minerals are found with cappelenite-(y)?+
What kind of rock does cappelenite-(y) form in?+
What is cappelenite-(y) used for?+
Find cappelenite-(y) on the map
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