Atencioite is a rare phosphate mineral member of the roscherite group, typically found as small bladed crystals or radiating clusters within complex pegmatite environments. It is chemically distinguished by its iron-rich composition compared to other group members and is primarily prized by advanced mineral collectors for its rarity.

Hardness

4.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareRoscherite Group family

Atencioite

Hardness: 4.5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this atencioite?

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 atencioite with a known reference. Atencioite sits at Mohs 4.5, 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: greenish brown.
5
Look at form & habit
Crystal system: triclinic. Typical habit: concretionary, spherical.

Often confused with

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

mineral

Roscherite

Mohs 4.5

How to tell apart: Streak differs, so Atencioite leaves white, Roscherite leaves light brown.

Often found alongside atencioite

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

All properties

Chemical formula: Ca₂Fe₃Mg₂Be₄(PO₄)₆(OH)₄·6H₂O
Mohs hardness: 4.5
Density: 2.84-2.86 g/cm³
Colors: Greenish brown
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Triclinic
Crystal habit: Concretionary, spherical
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Occurs in granite pegmatite

Where rockhounds find atencioite

Classic worldwide localities

Linopolis, Divino das Laranjeiras, Minas Gerais State, Brazil (type locality)

Field-hunting tip

Where it forms: Occurs in granite pegmatite. If you start seeing quartz, albite, muscovite in float, you are in the right ground. Typical habit: concretionary, spherical. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify atencioite?+

Mohs hardness is 4.5. Luster: vitreous. The streak is white. Common colors include greenish brown.

Where is atencioite found?+

Notable localities include Linopolis, Divino das Laranjeiras, Minas Gerais State, Brazil (type locality).

Is atencioite safe to handle?+

Atencioite contains beryllium. Wash your hands afterwards, never grind or breathe the dust, and store it apart from specimens you handle often.

What rocks look like atencioite?+

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

What minerals are found with atencioite?+

Atencioite commonly co-occurs with Quartz, Albite, Muscovite, Beryl. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does atencioite form in?+

Where it forms: Occurs in granite pegmatite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is atencioite used for?+

Atencioite is used in collector.

Find atencioite on the map

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