Gajardoite is an extremely rare manganese-aluminum arsenate mineral first identified in the Gajardo mine in Chile. It typically occurs as small, delicate, pseudo-hexagonal crystals found in association with secondary arsenic minerals in arid mining environments.

Hardness

2-3

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Gajardoite

Hardness: 2-3
Luster: Vitreous
Streak: White
Transparency: Transparent

No image

Is this gajardoite?

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 gajardoite with a known reference. Gajardoite sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Gajardoite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Gajardoite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, greenish-yellow.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular, pseudo-hexagonal crystals.

Often confused with

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

mineral

Pharmacosiderite

Mohs 2.5

How to tell apart: Luster reads vitreous on Gajardoite and adamantine on Pharmacosiderite.

How to tell apart: Luster reads vitreous on Gajardoite and vitreous to sub-adamantine on Scorodite.

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Often found alongside gajardoite

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

Quartz
mineral · Mohs 7

All properties

Chemical formula: Mn²⁺₅Al₆(AsO₄)₄(OH)₁₂·8H₂O
Mohs hardness: 2-3
Density: 2.81 g/cm³
Colors: Yellow Greenish-yellow
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Tabular, Pseudo-hexagonal Crystals
Cleavage: Perfect in One Direction
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Veins
Typical price: $50-300 per specimen

Where rockhounds find gajardoite

Classic worldwide localities

Gajardo mine, Chile

Field-hunting tip

Look in hydrothermal veins country, the host setting where gajardoite typically forms. If you start seeing arsenates, quartz in float, you are in the right ground. Field specimens usually show a tabular, pseudo-hexagonal crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify gajardoite?+

Mohs hardness is 2-3. It typically shows a vitreous luster. The streak is white. Common colors include yellow, greenish-yellow.

Where is gajardoite found?+

Notable localities include Gajardo mine, Chile.

How much is gajardoite 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 gajardoite safe to handle?+

It contains toxic constituents. Contains arsenic, which is toxic. Wash hands thoroughly after handling and avoid ingestion or inhalation of dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like gajardoite?+

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

What minerals are found with gajardoite?+

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

What kind of rock does gajardoite form in?+

Gajardoite typically forms in hydrothermal veins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is gajardoite used for?+

Gajardoite is used in collector.

Find gajardoite on the map

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