Hedegaardite is a rare calcium sodium magnesium phosphate. It was approved as a distinct mineral species in 2014. It was first described from Punta de Lobos, Mejillones, Antofagasta Region, Chile.

Hardness

Mohs

Luster

Vitreous

Transparency

Transparent

mineralrareVivianite Group family

Hedegaardite

Hedegaardite is a rare calcium sodium magnesium phosphate. It was approved as a distinct mineral species in 2014. It was first described from Punta de Lobos, Mejillones, Antofagasta Region, Chile.

Hardness: 3
Luster: Vitreous
Transparency: Transparent

Is this hedegaardite?

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 hedegaardite with a known reference. Hedegaardite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
2
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
3
Match the color range
Compare against the expected color range: yellow, brownish-yellow.
4
Look at form & habit
Crystal system: trigonal. Typical habit: prismatic crystals.

Often confused with

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

mineral

Vivianite

Mohs 1.5-2

How to tell apart: Hedegaardite is noticeably harder (Mohs 3 vs. 1.5-2).

How to tell apart: Hedegaardite is noticeably harder (Mohs 3 vs. 1.5-2); luster reads vitreous on Hedegaardite and submetallic on Metavivianite.

Compare →

Often found alongside hedegaardite

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

All properties

Chemical formula: (Ca,Na)₉(Ca,Na)Mg(PO₄)₆(PO₃OH)
Mohs hardness: 3
Colors: Yellow Brownish-yellow
Luster: Vitreous
Transparency: Transparent
Crystal system: Trigonal
Crystal habit: Prismatic crystals
Rarity: Rare
Uses: Collector
Host rock: sedimentary deposits

Where rockhounds find hedegaardite

Classic worldwide localities

Punta de Lobos, Rio Seco, 90 km south of Iquique, Tarapacá Region and Cerro Mejillones, Mejillones Peninsula, Mejillones, Antofagasta Region, Chile

Field-hunting tip

Where it forms: sedimentary deposits. If you start seeing vivianite, siderite, quartz in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify hedegaardite?+

Mohs hardness is 3. Luster: vitreous. Common colors include yellow, brownish-yellow.

Where is hedegaardite found?+

Notable localities include Punta de Lobos, Rio Seco, 90 km south of Iquique, Tarapacá Region and Cerro Mejillones, Mejillones Peninsula, Mejillones, Antofagasta Region, Chile.

What rocks look like hedegaardite?+

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

What minerals are found with hedegaardite?+

Hedegaardite commonly co-occurs with Vivianite, Siderite, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does hedegaardite form in?+

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

What is hedegaardite used for?+

Hedegaardite is used in collector.

Find hedegaardite on the map

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