Llantenesite is a rare copper aluminum selenate. It was approved as a distinct mineral species in 2019. It was first described from Mina San Pedro, Vinchina Department, La Rioja Province, Argentina.

Hardness

2.5-3

Mohs

Luster

Pearly

Transparency

Translucent

mineralrareCopiapite Group family

Llantenesite

Llantenesite is a rare copper aluminum selenate. It was approved as a distinct mineral species in 2019. It was first described from Mina San Pedro, Vinchina Department, La Rioja Province, Argentina.

Hardness: 2.5-3
Luster: Pearly
Transparency: Translucent

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Is this llantenesite?

4-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 llantenesite with a known reference. Llantenesite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
2
Read the luster
Hold the specimen under a strong light. Luster: pearly.
3
Match the color range
Compare against the expected color range: yellow, yellowish-orange.
4
Look at form & habit
Crystal system: trigonal. Typical habit: tabular crystals, crusts, efflorescent aggregates.

Often confused with

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

How to tell apart: Luster reads pearly on Llantenesite and earthy on Aluminocopiapite.

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Often found alongside llantenesite

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

All properties

Chemical formula: Cu₆Al[SeO₄](OH)₁₂Cl·3H₂O
Mohs hardness: 2.5-3
Colors: Yellow Yellowish-orange
Luster: Pearly
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Tabular crystals, crusts, efflorescent aggregates
Rarity: Rare
Uses: Collector
Host rock: oxidized zones of sulfide ore deposits

Where rockhounds find llantenesite

Classic worldwide localities

Mina San Pedro, Cuesta de Los Llantenes mining district, northwest Jagüé, Vinchina Department, La Rioja Province, Argentina

Field-hunting tip

Where it forms: oxidized zones of sulfide ore deposits. If you start seeing copiapite, jarosite, melanterite in float, you are in the right ground. Typical habit: tabular crystals, crusts, efflorescent aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify llantenesite?+

Mohs hardness is 2.5-3. Luster: pearly. Common colors include yellow, yellowish-orange.

Where is llantenesite found?+

Notable localities include Mina San Pedro, Cuesta de Los Llantenes mining district, northwest Jagüé, Vinchina Department, La Rioja Province, Argentina.

Is llantenesite safe to handle?+

Llantenesite contains copper and selenium. Contains selenium, which is toxic if ingested or inhaled as dust. Wash hands thoroughly after handling and avoid creating dust.

What rocks look like llantenesite?+

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

What minerals are found with llantenesite?+

Llantenesite commonly co-occurs with Copiapite, Jarosite, Melanterite, Gypsum. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does llantenesite form in?+

Where it forms: oxidized zones of sulfide ore deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is llantenesite used for?+

Llantenesite is used in collector.

Find llantenesite on the map

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