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.

Hardness

6.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrare

Cappelenite-(Y)

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

Is this cappelenite-(y)?

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 cappelenite-(y) with a known reference. Cappelenite-(Y) sits at Mohs 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. Cappelenite-(Y) leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Cappelenite-(Y) typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: greenish-brown, brown, yellowish-brown.
5
Look at form & habit
Crystal system: trigonal. Typical habit: prismatic crystals.

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 — Cappelenite-(Y) leaves white, Allanite leaves gray; luster reads vitreous on Cappelenite-(Y) and submetallic on Allanite.

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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: Ba(Y,REE)₆Si₃B₆O₂₄F₂
Mohs hardness: 6.5
Density: 4.45 g/cm³
Colors: Greenish-brown Brown Yellowish-brown
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Prismatic Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Syenite Pegmatites
Typical price: $50-300 per specimen

Where rockhounds find cappelenite-(y)

Classic worldwide localities

Låven, Langesundsfjord, Norway
Kola Peninsula, Russia
Mount Saint-Hilaire, Canada

Field-hunting tip

Look in syenite pegmatites country — that is the host setting where cappelenite-(y) typically forms. If you start seeing aegirine, microcline, nepheline in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify cappelenite-(y)?+

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

Where is cappelenite-(y) found?+

Notable localities include Låven, Langesundsfjord, Norway; Kola Peninsula, Russia; Mount Saint-Hilaire, Canada.

How much is cappelenite-(y) worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is cappelenite-(y) safe to handle?+

This mineral is radioactive. Contains minor rare earth elements and thorium which may result in weak radioactivity. Handle with care, avoid creating dust, and store in an appropriate container away from prolonged personal contact. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like cappelenite-(y)?+

Cappelenite-(Y) is most often confused with Gadolinite-(Y), Allanite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with cappelenite-(y)?+

Cappelenite-(Y) commonly co-occurs with Aegirine, Microcline, Nepheline, Eudialyte, Arfvedsonite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does cappelenite-(y) form in?+

Cappelenite-(Y) typically forms in syenite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is cappelenite-(y) used for?+

Cappelenite-(Y) is used in collector.

Find cappelenite-(y) on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.