Amarillite is an extremely rare thallium-bearing sulfate mineral primarily known from the copper mines of northern Chile. It typically forms as delicate, pale yellow prismatic crystals or crusts within the oxidized zones of ore deposits. Due to its thallium content and rarity, it is a specialized collector's mineral that requires careful handling.

Hardness

2.5-3

Mohs

Luster

Vitreous to adamantine

Streak

White

Transparency

Transparent

mineralrare

Amarillite

Hardness: 2.5-3
Luster: Vitreous to adamantine
Streak: White
Transparency: Transparent

Is this amarillite?

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 amarillite with a known reference. Amarillite sits at Mohs 2.5-3, 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 to adamantine.
4
Match the color range
Compare against the expected color range: greenish yellow, light yellow.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: prismatic crystals, crusts.

Often confused with

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

mineral

Pickeringite

Mohs 1.5

How to tell apart: Amarillite is noticeably harder (Mohs 2.5-3 vs. 1.5).

How to tell apart: Amarillite is noticeably harder (Mohs 2.5-3 vs. 1.5).

Compare →

Often found alongside amarillite

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

Coquimbite
mineral · Mohs 2.5

All properties

Chemical formula: NaFe³⁺(SO₄)₂·6H₂O
Mohs hardness: 2.5-3
Density: 2.19-2.20 g/cm³
Colors: Greenish yellow Light yellow
Streak: White
Luster: Vitreous to adamantine
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Prismatic crystals, crusts
Cleavage: {110}, good, but difficult
Rarity: Rare
Uses: Collector
Host rock: Formed in the oxidation zones of sulfide deposits

Where rockhounds find amarillite

Classic worldwide localities

Tierra Amarilla, southeast of Copiapó, Atacama, Chile
Xitieshan Pb–Zn mine, south of Mt. Qilianshan, Chaidamu, Qinghai Province, China

Field-hunting tip

Where it forms: Formed in the oxidation zones of sulfide deposits. If you start seeing coquimbite in float, you are in the right ground. Typical habit: prismatic crystals, crusts. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify amarillite?+

Mohs hardness is 2.5-3. Luster: vitreous to adamantine. The streak is white. Common colors include greenish yellow, light yellow.

Where is amarillite found?+

Notable localities include Tierra Amarilla, southeast of Copiapó, Atacama, Chile; Xitieshan Pb–Zn mine, south of Mt. Qilianshan, Chaidamu, Qinghai Province, China.

What rocks look like amarillite?+

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

What minerals are found with amarillite?+

Amarillite commonly co-occurs with Coquimbite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does amarillite form in?+

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

What is amarillite used for?+

Amarillite is used in collector.

Find amarillite on the map

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