Lautarite is a rare calcium iodate mineral found primarily in the nitrate deposits of the Atacama Desert. It typically forms colorless to yellowish prismatic crystals that are highly soluble in water, making it a challenging mineral to collect and store in humid environments.

Hardness

3.5-4

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Lautarite

Hardness: 3.5-4
Luster: Vitreous
Streak: White
Transparency: Transparent

No image

Is this lautarite?

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 lautarite with a known reference. Lautarite sits at Mohs 3.5-4, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: colorless, yellowish, light yellow.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: prismatic crystals, massive, granular.

Often confused with

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

mineral

Dietzeite

Mohs 3.5

How to tell apart: Streak differs, so Lautarite leaves white, Dietzeite leaves light yellow.

How to tell apart: Lautarite is noticeably harder (Mohs 3.5-4 vs. 1.5-2); luster reads vitreous on Lautarite and subvitreous, pearly on {010} cleavages, silky if fibrous on Gypsum.

Compare →

Often found alongside lautarite

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

All properties

Chemical formula: Ca(IO₃)₂
Mohs hardness: 3.5-4
Density: 4.59 g/cm³
Colors: Colorless Yellowish Light yellow
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Prismatic crystals, massive, granular
Cleavage: On {011}, good; {100}, {110}, interrupted
Rarity: Rare
Uses: Collector
Host rock: Coating fractures or embedded in gypsum in the nitrate deposits

Where rockhounds find lautarite

Classic worldwide localities

Pampa del Pique III, about one km north of Oficina Lautaro, Taltal district, Antofagasta, Chile

Field-hunting tip

Where it forms: Coating fractures or embedded in gypsum in the nitrate deposits. If you start seeing gypsum, brüggenite, dietzeite in float, you are in the right ground. Typical habit: prismatic crystals, massive, granular. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify lautarite?+

Mohs hardness is 3.5-4. Luster: vitreous. The streak is white. Common colors include colorless, yellowish, light yellow.

Where is lautarite found?+

Notable localities include Pampa del Pique III, about one km north of Oficina Lautaro, Taltal district, Antofagasta, Chile.

Is lautarite safe to handle?+

Contains iodine and is potentially toxic if ingested or inhaled as dust; wash hands thoroughly after handling specimens.

What rocks look like lautarite?+

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

What minerals are found with lautarite?+

Lautarite commonly co-occurs with Gypsum, Brüggenite, Dietzeite, Nitratine, Anhydrite, Hydroboracite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does lautarite form in?+

Where it forms: Coating fractures or embedded in gypsum in the nitrate deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is lautarite used for?+

Lautarite is used in collector.

Find lautarite on the map

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