Sobolevite is an extremely rare silicate mineral found in the hyper-alkaline environments of the Kola Peninsula. It typically occurs as small tabular crystals or granular masses within highly evolved pegmatitic pockets alongside complex accessory minerals.

Hardness

~4.5-5

Mohs

Luster

Metallic, resinous, or pearly on (001)

Streak

Yellowish brown

Transparency

Semitransparent

mineralrare

Sobolevite

Hardness: ~4.5-5
Luster: Metallic, resinous, or pearly on (001)
Streak: Yellowish brown
Transparency: Semitransparent

Is this sobolevite?

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 sobolevite with a known reference. Sobolevite sits at Mohs ~4.5-5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: yellowish brown.
3
Read the luster
Hold the specimen under a strong light. Luster: metallic, resinous, or pearly on (001).
4
Match the color range
Compare against the expected color range: brown.
5
Look at form & habit
Crystal system: triclinic. Typical habit: massive, platy.

Often confused with

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

mineral

Lomonosovite

Mohs 3-4

How to tell apart: Streak differs, so Sobolevite leaves yellowish brown, Lomonosovite leaves light rose-cinnamon; luster reads metallic, resinous, or pearly on (001) on Sobolevite and vitreous to adamantine on cleavages, greasy on fractures on Lomonosovite.

How to tell apart: Sobolevite is noticeably harder (Mohs ~4.5-5 vs. 2-3); streak differs, so Sobolevite leaves yellowish brown, Murmanite leaves white; luster reads metallic, resinous, or pearly on (001) on Sobolevite and vitreous on cleavages, greasy on fractures on Murmanite.

Compare →

Often found alongside sobolevite

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

All properties

Chemical formula: Na₆(Na₂Ca)(NaCaMn)Na₂Ti₂Na₂(TiMn)(Si₂O₇)₂(PO₄)₄O₂(OF)F₂
Mohs hardness: ~4.5-5
Density: 3.03 g/cm³
Colors: Brown
Streak: Yellowish brown
Luster: Metallic, resinous, or pearly on (001)
Transparency: Semitransparent
Crystal system: Triclinic
Crystal habit: Massive, platy
Cleavage: Perfect on {001}, distinct on {110}
Rarity: Rare
Uses: Collector
Host rock: In alkalic pegmatite, cutting sodalite-cancrinite syenite, in a differentiated alkalic massif

Where rockhounds find sobolevite

Classic worldwide localities

Mt. Alluaiv, Lovozero massif, Kola Peninsula, Russia

Field-hunting tip

Where it forms: In alkalic pegmatite, cutting sodalite-cancrinite syenite, in a differentiated alkalic massif. If you start seeing lamprophyllite, lomonosovite in float, you are in the right ground. Typical habit: massive, platy. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify sobolevite?+

Mohs hardness is ~4.5-5. Luster: metallic, resinous, or pearly on (001). The streak is yellowish brown. Common colors include brown.

Where is sobolevite found?+

Notable localities include Mt. Alluaiv, Lovozero massif, Kola Peninsula, Russia.

What rocks look like sobolevite?+

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

What minerals are found with sobolevite?+

Sobolevite commonly co-occurs with Lamprophyllite, Lomonosovite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does sobolevite form in?+

Where it forms: In alkalic pegmatite, cutting sodalite-cancrinite syenite, in a differentiated alkalic massif. Working float back to the host body is the standard way to chase a fresh occurrence.

What is sobolevite used for?+

Sobolevite is used in collector.

Find sobolevite on the map

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