Pseudolyonsite is an extremely rare copper iron vanadate that typically forms as small, yellow, tabular crystals or crusts within volcanic fumaroles. It is primarily known from the Izalco Volcano in El Salvador, where it occurs as a sublimate from hot volcanic gases.

Hardness

Mohs

Luster

Resinous

Streak

Yellow

Transparency

Translucent

mineralrare

Pseudolyonsite

Hardness: 3
Luster: Resinous
Streak: Yellow
Transparency: Translucent

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Is this pseudolyonsite?

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 pseudolyonsite with a known reference. Pseudolyonsite sits at Mohs 3 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Pseudolyonsite leaves a yellow streak.
3
Read the luster
Hold the specimen under a strong light. Pseudolyonsite typically shows a resinous luster.
4
Match the color range
Compare against the expected color range: yellow, brownish-yellow.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: tabular crystals, crusts.

Often confused with

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

mineral

Lyonsite

Mohs 3-3.5

How to tell apart: Luster reads resinous on Pseudolyonsite and vitreous on Lyonsite.

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Often found alongside pseudolyonsite

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

All properties

Chemical formula: Cu₃Fe₄(VO₄)₆
Mohs hardness: 3
Density: 3.37 g/cm³
Colors: Yellow Brownish-yellow
Streak: Yellow
Luster: Resinous
Transparency: Translucent
Crystal system: Orthorhombic
Crystal habit: Tabular Crystals, Crusts
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Fumarole Deposits
Typical price: $50-300 per specimen

Where rockhounds find pseudolyonsite

Classic worldwide localities

Izalco Volcano, El Salvador

Field-hunting tip

Look in fumarole deposits country — that is the host setting where pseudolyonsite typically forms. If you start seeing lyonsite, thenardite, metavoltine in float, you are in the right ground. Field specimens usually show a tabular crystals, crusts habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify pseudolyonsite?+

Mohs hardness is 3. It typically shows a resinous luster. The streak is yellow. Common colors include yellow, brownish-yellow.

Where is pseudolyonsite found?+

Notable localities include Izalco Volcano, El Salvador.

How much is pseudolyonsite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is pseudolyonsite safe to handle?+

It contains toxic constituents. Contains copper and vanadium. Wash hands thoroughly after handling and avoid inhaling dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like pseudolyonsite?+

Pseudolyonsite is most often confused with Lyonsite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with pseudolyonsite?+

Pseudolyonsite commonly co-occurs with Lyonsite, Thenardite, Metavoltine. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does pseudolyonsite form in?+

Pseudolyonsite typically forms in fumarole deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is pseudolyonsite used for?+

Pseudolyonsite is used in collector.

Find pseudolyonsite on the map

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