Filatovite is an extremely rare arsenic-bearing feldspar found exclusively in the fumaroles of the Tolbachik volcano in Russia. It typically occurs as small, clear, tabular crystals associated with other unusual volcanic minerals. Due to its arsenic content, it is strictly a mineralogical specimen for advanced collectors and requires careful handling.

Hardness

5-6

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareFeldspar Group family

Filatovite

Hardness: 5-6
Luster: Vitreous
Streak: White
Transparency: Transparent

No image

Is this filatovite?

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 filatovite with a known reference. Filatovite sits at Mohs 5-6, 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.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: prismatic.

Often confused with

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

Often found alongside filatovite

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

All properties

Chemical formula: K(AlZn)₂(As,Si)₂O₈
Mohs hardness: 5-6
Density: 2.92 g/cm³
Colors: Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Prismatic
Cleavage: Good on {100}
Rarity: Rare
Uses: Collector
Host rock: A product of fumarolic activity

Where rockhounds find filatovite

Classic worldwide localities

The second cinder cone of the North Breach of Great fissure Tolbachik eruption (GFTE), Kamchatka Peninsula, Russia (type locality)

Field-hunting tip

Where it forms: A product of fumarolic activity. If you start seeing alumokluchevskite, lammerite, johillerite 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 filatovite?+

Mohs hardness is 5-6. Luster: vitreous. The streak is white. Common colors include colorless.

Where is filatovite found?+

Notable localities include The second cinder cone of the North Breach of Great fissure Tolbachik eruption (GFTE), Kamchatka Peninsula, Russia (type locality).

Is filatovite safe to handle?+

Filatovite contains arsenic and calls for real care. Contains arsenic, which is toxic. Handle with care, wash hands after handling, and avoid inhaling dust.

What rocks look like filatovite?+

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

What minerals are found with filatovite?+

Filatovite commonly co-occurs with Alumokluchevskite, Lammerite, Johillerite, Sylvite, Hematite, Tenorite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does filatovite form in?+

Where it forms: A product of fumarolic activity. Working float back to the host body is the standard way to chase a fresh occurrence.

What is filatovite used for?+

Filatovite is used in collector.

Find filatovite on the map

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