Achyrophanite is a rare potassium sodium iron arsenate. It was approved as a distinct mineral species in 2018. It was first described from the Arsenatnaya fumarole, Kamchatka peninsula, Far-Eastern Region, Russia.

Hardness

6.5-7.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareGarnet Group family

Achyrophanite

Hardness: 6.5-7.5
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this achyrophanite?

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 achyrophanite with a known reference. Achyrophanite sits at Mohs 6.5-7.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Achyrophanite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Achyrophanite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: dark brown, brownish-red.
5
Look at form & habit
Crystal system: orthorhombic.

Often confused with

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

mineral

Almandine

Mohs 7-7.5

How to tell apart: Luster reads vitreous on Achyrophanite and vitreous to subresinous on Almandine.

How to tell apart: Luster reads vitreous on Achyrophanite and adamantine to resinous to dull on Andradite.

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Often found alongside achyrophanite

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

All properties

Chemical formula: (K,Na)₃(Fe³⁺,Ti,Al,Mg)₅O₂(AsO₄)₅
Mohs hardness: 6.5-7.5
Density: 3.8-4.1 g/cm³
Colors: Dark Brown Brownish-red
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Orthorhombic
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Metamorphic Rocks

Where rockhounds find achyrophanite

Classic worldwide localities

Arsenatnaya fumarole, Far-Eastern Region, Russia

Field-hunting tip

Look in metamorphic rocks country, the host setting where achyrophanite typically forms. If you start seeing quartz, biotite, feldspar in float, you are in the right ground.

Common questions

How do you identify achyrophanite?+

Mohs hardness is 6.5-7.5. It typically shows a vitreous luster. The streak is white. Common colors include dark brown, brownish-red.

Where is achyrophanite found?+

Notable localities include Arsenatnaya fumarole, Far-Eastern Region, Russia.

Is achyrophanite safe to handle?+

It contains toxic constituents. Contains arsenic, which is toxic if ingested or inhaled as dust. Wash hands thoroughly after handling and avoid creating dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like achyrophanite?+

Achyrophanite is most often confused with Almandine, Spessartine, Andradite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with achyrophanite?+

Achyrophanite commonly co-occurs with Quartz, Biotite, Feldspar. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does achyrophanite form in?+

Achyrophanite typically forms in metamorphic rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is achyrophanite used for?+

Achyrophanite is used in collector.

Find achyrophanite on the map

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