Magnesiofluckite is an extremely rare arsenic-bearing mineral often found as colorless to white bladed crystals. It is primarily identified in hydrothermal mining dumps and is best suited for advanced mineral collections due to its rarity and arsenic content.

Hardness

2.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareFluckite Group family

Magnesiofluckite

Hardness: 2.5
Luster: Vitreous
Streak: White
Transparency: Transparent

No image

Is this magnesiofluckite?

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 magnesiofluckite with a known reference. Magnesiofluckite 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: 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.
5
Look at form & habit
Crystal system: triclinic. Typical habit: bladed crystals.

Often confused with

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

mineral

Fluckite

Mohs 3.5-4

How to tell apart: Fluckite is the harder of the two (Mohs 3.5-4 vs. 2.5).

Often found alongside magnesiofluckite

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

All properties

Chemical formula: CaMg(AsO₃OH)₂·2H₂O
Mohs hardness: 2.5
Density: 2.93 g/cm³
Colors: Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Triclinic
Crystal habit: Bladed crystals
Cleavage: Good on {100}, perfect on {010}
Rarity: Rare
Uses: Collector
Host rock: hydrothermal veins

Where rockhounds find magnesiofluckite

Classic worldwide localities

Torrecillas mine, northern Atacama Desert, Salar Grande, Iquique Province, Tarapacá Region, Chile

Field-hunting tip

Where it forms: hydrothermal veins. If you start seeing camanchacaite, anhydrite, gypsum in float, you are in the right ground. Typical habit: bladed crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify magnesiofluckite?+

Mohs hardness is 2.5. Luster: vitreous. The streak is white. Common colors include colorless.

Where is magnesiofluckite found?+

Notable localities include Torrecillas mine, northern Atacama Desert, Salar Grande, Iquique Province, Tarapacá Region, Chile.

Is magnesiofluckite safe to handle?+

Magnesiofluckite contains arsenic and calls for real care. Contains arsenic. Wash hands thoroughly after handling and avoid inhaling dust or ingesting particles.

What rocks look like magnesiofluckite?+

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

What minerals are found with magnesiofluckite?+

Magnesiofluckite commonly co-occurs with Camanchacaite, Anhydrite, Gypsum, Halite, Talmessite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does magnesiofluckite form in?+

Where it forms: hydrothermal veins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is magnesiofluckite used for?+

Magnesiofluckite is used in collector.

Find magnesiofluckite on the map

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