Alflarsenite is a rare beryllium silicate mineral found primarily in the alkaline pegmatites of the Langesundsfjord district in Norway. It typically occurs as small, colorless to white equant crystals and is best identified by its strong blue fluorescence under ultraviolet light.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent to transparent

mineralrare

Alflarsenite

Hardness: ~4
Luster: Vitreous
Streak: White
Transparency: Translucent to transparent

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Is this alflarsenite?

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 alflarsenite with a known reference. Alflarsenite sits at Mohs ~4, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: colorless, white.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: equant crystals, massive.

Often confused with

Alflarsenite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Quartz

Mohs 7

How to tell apart: Quartz is the harder of the two (Mohs 7 vs. ~4).

How to tell apart: Feldspar is the harder of the two (Mohs 6 vs. ~4).

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Often found alongside alflarsenite

Minerals reported to co-occur with alflarsenite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: NaCa₂Be₃Si₄O₁₃(OH)·2H₂O
Mohs hardness: ~4
Density: 2.605 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous
Transparency: Translucent to transparent
Crystal system: Monoclinic
Crystal habit: Equant crystals, massive
Cleavage: None observed
Fluorescence: Bright blue under UV
Rarity: Rare
Uses: Collector
Host rock: A late-stage hydrothermal mineral in a syenitic pegmatite in larvikite

Where rockhounds find alflarsenite

Classic worldwide localities

Tuften larvikite quarry, Tvedalen, Larvik, Vestfold, south Norway

Field-hunting tip

Where it forms: A late-stage hydrothermal mineral in a syenitic pegmatite in larvikite. If you start seeing calcite, analcime, k-feldspar in float, you are in the right ground. Typical habit: equant crystals, massive. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify alflarsenite?+

Mohs hardness is ~4. Luster: vitreous. The streak is white. Common colors include colorless, white.

Where is alflarsenite found?+

Notable localities include Tuften larvikite quarry, Tvedalen, Larvik, Vestfold, south Norway.

Is alflarsenite safe to handle?+

Alflarsenite contains beryllium. Wash your hands afterwards, never grind or breathe the dust, and store it apart from specimens you handle often.

What rocks look like alflarsenite?+

Alflarsenite is most often confused with Quartz, Feldspar. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with alflarsenite?+

Alflarsenite commonly co-occurs with Calcite, Analcime, K-feldspar. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does alflarsenite form in?+

Where it forms: A late-stage hydrothermal mineral in a syenitic pegmatite in larvikite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is alflarsenite used for?+

Alflarsenite is used in collector.

Find alflarsenite on the map

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