Asbecasite is an exceptionally rare beryllium-arsenic silicate found primarily in the Lengenbach Quarry of Switzerland. It typically occurs as small, tabular, yellowish-brown crystals embedded within dolomitic marble or associated with complex sulfosalt minerals.

Hardness

6.5-7

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Asbecasite

Hardness: 6.5-7
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this asbecasite?

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 asbecasite with a known reference. Asbecasite sits at Mohs 6.5-7, 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: lemon, brownish.
5
Look at form & habit
Crystal system: trigonal. Typical habit: rhombohedral crystals.

Often confused with

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

mineral

Titanite

Mohs 5-5.5

How to tell apart: Asbecasite is noticeably harder (Mohs 6.5-7 vs. 5-5.5); luster reads vitreous on Asbecasite and adamantine to resinous on Titanite.

Often found alongside asbecasite

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

All properties

Chemical formula: Ca₃TiAs₆Be₂Si₂O₂₀
Mohs hardness: 6.5-7
Density: 3.70 g/cm³
Colors: Lemon Brownish
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Trigonal
Crystal habit: Rhombohedral crystals
Cleavage: Rhombohedral
Rarity: Rare
Uses: Collector
Host rock: On cleft faces in orthogneiss (Cherbadung, Switzerland)

Where rockhounds find asbecasite

Classic worldwide localities

East flank of Pizzo Cervandone, Alpe Devero, Val d'Aosta, Italy (type locality)

Field-hunting tip

Where it forms: On cleft faces in orthogneiss (Cherbadung, Switzerland). If you start seeing magnetite, hematite, titanite in float, you are in the right ground. Typical habit: rhombohedral crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify asbecasite?+

Mohs hardness is 6.5-7. Luster: vitreous. The streak is white. Common colors include lemon, brownish.

Where is asbecasite found?+

Notable localities include East flank of Pizzo Cervandone, Alpe Devero, Val d'Aosta, Italy (type locality).

Is asbecasite safe to handle?+

Asbecasite contains arsenic and beryllium and calls for real care. Contains arsenic, a toxic element. Handle with care, avoid creating dust, and wash hands thoroughly after handling.

What rocks look like asbecasite?+

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

What minerals are found with asbecasite?+

Asbecasite commonly co-occurs with Magnetite, Hematite, Titanite, Apatite, Anatase, Malachite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does asbecasite form in?+

Where it forms: On cleft faces in orthogneiss (Cherbadung, Switzerland). Working float back to the host body is the standard way to chase a fresh occurrence.

What is asbecasite used for?+

Asbecasite is used in collector.

Find asbecasite on the map

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