Chongite is a rare calcium magnesium arsenate that forms colorless prismatic crystals. Associated minerals include arsenolite, gajardoite and talmessite. It was first described from Torrecillas mine, northern Atacama Desert, Iquique Province, Chile.

Hardness

2-3

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Chongite

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

No image

Is this chongite?

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 chongite with a known reference. Chongite 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. Chongite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Chongite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: prismatic crystals.

Often confused with

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

Often found alongside chongite

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

All properties

Chemical formula: Ca₃Mg₂(AsO₄)₂(AsO₃OH)₂·4H₂O
Mohs hardness: 2-3
Density: 3.09 g/cm³
Colors: Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Prismatic Crystals
Cleavage: Good On {100}
Rarity: Rare
Uses: Collector
Host rock: Guano Deposits

Where rockhounds find chongite

Classic worldwide localities

Torrecillas mine, Iquique Province, Chile

Field-hunting tip

Look in guano deposits country, the host setting where chongite typically forms. If you start seeing brushite, struvite in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify chongite?+

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

Where is chongite found?+

Notable localities include Torrecillas mine, Iquique Province, Chile.

Is chongite safe to handle?+

It contains toxic constituents. Contains arsenic, which is toxic if ingested or inhaled as dust. Wash hands thoroughly after handling and avoid creating dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like chongite?+

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

What minerals are found with chongite?+

Chongite commonly co-occurs with brushite, struvite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does chongite form in?+

Chongite typically forms in guano deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is chongite used for?+

Chongite is used in collector.

Find chongite on the map

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