Mendozavilite-NaCu is an extremely rare secondary molybdate mineral typically found as earthy crusts or powdery coatings in oxidized ore deposits. It is best identified by its association with other molybdenum minerals in arid environments, though positive identification usually requires powder X-ray diffraction analysis.

Hardness

~2.5

Mohs

Luster

Vitreous to subadamantine

Streak

Colorless to very pale green

Transparency

Transparent

mineralrareMendozavilite Group family

Mendozavilite-NaCu

Hardness: ~2.5
Luster: Vitreous to subadamantine
Streak: Colorless to very pale green
Transparency: Transparent

Is this mendozavilite-nacu?

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 mendozavilite-nacu with a known reference. Mendozavilite-NaCu sits at Mohs ~2.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: colorless to very pale green.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous to subadamantine.
4
Match the color range
Compare against the expected color range: lime green.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: powdery, earthy, granular aggregates.

Often confused with

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

mineral

Ferrimolybdite

Mohs 1-2

How to tell apart: Streak differs, so Mendozavilite-NaCu leaves colorless to very pale green, Ferrimolybdite leaves pale yellow; luster reads vitreous to subadamantine on Mendozavilite-NaCu and adamantine to silky, earthy on Ferrimolybdite.

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Often found alongside mendozavilite-nacu

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

All properties

Chemical formula: [Na₂(H₂O)₁₅Cu(H₂O)₆][Mo₈P₂Fe₃O₃₄(OH)₃]
Mohs hardness: ~2.5
Density: 2.824 g/cm³
Colors: Lime green
Streak: Colorless to very pale green
Luster: Vitreous to subadamantine
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Powdery, earthy, granular aggregates
Cleavage: Perfect on {001}
Rarity: Rare
Uses: Collector
Host rock: In the oxidized zone of porphyry copper deposit as thin vein fillings and well-formed crystals in cavities

Where rockhounds find mendozavilite-nacu

Classic worldwide localities

Lomas Bayas mine, 93 km east northeast of Antofagasta, Antofagasta Province, Chile

Field-hunting tip

Where it forms: In the oxidized zone of porphyry copper deposit as thin vein fillings and well-formed crystals in cavities. If you start seeing quartz, feruvite, muscovite in float, you are in the right ground. Typical habit: powdery, earthy, granular aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify mendozavilite-nacu?+

Mohs hardness is ~2.5. Luster: vitreous to subadamantine. The streak is colorless to very pale green. Common colors include lime green.

Where is mendozavilite-nacu found?+

Notable localities include Lomas Bayas mine, 93 km east northeast of Antofagasta, Antofagasta Province, Chile.

Is mendozavilite-nacu safe to handle?+

Mendozavilite-NaCu contains copper. Wash your hands afterwards, never grind or breathe the dust, and store it apart from specimens you handle often.

What rocks look like mendozavilite-nacu?+

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

What minerals are found with mendozavilite-nacu?+

Mendozavilite-NaCu commonly co-occurs with Quartz, Feruvite, Muscovite, Pyrite, Chalcopyrite, Covellite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does mendozavilite-nacu form in?+

Where it forms: In the oxidized zone of porphyry copper deposit as thin vein fillings and well-formed crystals in cavities. Working float back to the host body is the standard way to chase a fresh occurrence.

What is mendozavilite-nacu used for?+

Mendozavilite-NaCu is used in collector.

Find mendozavilite-nacu on the map

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