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Hydroxycalcioroméite is a rare member of the pyrochlore supergroup, typically forming distinct octahedral crystals in manganese-rich metamorphic deposits. It is often found in association with other rare manganese minerals and is prized by advanced micromount collectors for its aesthetic crystal form.

Hardness
5.5
Mohs
Luster
Vitreous to resinous
Streak
Pale yellowish brown
Transparency
Translucent

Is this hydroxycalcioroméite?

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 hydroxycalcioroméite with a known reference. Hydroxycalcioroméite sits at Mohs 5.5, softer than the next harder reference, harder than the previous one.
  • 2
    Check the streak
    Drag the specimen across an unglazed porcelain plate. Streak: pale yellowish brown.
  • 3
    Read the luster
    Hold the specimen under a strong light. Luster: vitreous to resinous.
  • 4
    Match the color range
    Compare against the expected color range: honey-yellow, amber-yellow, yellowish brown.
  • 5
    Look at form & habit
    Crystal system: cubic. Typical habit: octahedral crystals, massive.

Often confused with

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

Dark brown pyrochlore octahedron
mineral
Pyrochlore
Mohs 5-5.5

How to tell apart: Streak differs, so Hydroxycalcioroméite leaves pale yellowish brown, Pyrochlore leaves brown.

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Often found alongside hydroxycalcioroméite

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

All properties

Chemical formula
(Ca,Sb)₂(Sb,Ti)₂O₆(OH)
Mohs hardness
5.5
Density
4.950 g/cm³
Colors
Honey-yellowAmber-yellowYellowish brown
Streak
Pale yellowish brown
Luster
Vitreous to resinous
Transparency
Translucent
Crystal system
Cubic
Crystal habit
Octahedral crystals, massive
Cleavage
{111}, nearly perfect
Rarity
Rare
Uses
Collector
Host rock
In eluvial sands (Tripuhy, Brazil)

Where rockhounds find hydroxycalcioroméite

Classic worldwide localities

  • Tripuhy cinnabar mine, Ouro Prêto, Minas Gerais, Brazil
  • Miniera del Tafone, Grosseto, Tuscany, Italy

Field-hunting tip

Where it forms: In eluvial sands (Tripuhy, Brazil). If you start seeing mica, cinnabar, tripuhyite in float, you are in the right ground. Typical habit: octahedral crystals, massive. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify hydroxycalcioroméite?+
Mohs hardness is 5.5. Luster: vitreous to resinous. The streak is pale yellowish brown. Common colors include honey-yellow, amber-yellow, yellowish brown.
Where is hydroxycalcioroméite found?+
Notable localities include Tripuhy cinnabar mine, Ouro Prêto, Minas Gerais, Brazil; Miniera del Tafone, Grosseto, Tuscany, Italy.
Is hydroxycalcioroméite safe to handle?+
Hydroxycalcioroméite contains antimony. Contains antimony, which is toxic if ingested or inhaled as dust; wash hands thoroughly after handling specimens.
What rocks look like hydroxycalcioroméite?+
Hydroxycalcioroméite is most often confused with Pyrochlore. A quick hardness test and a streak check separate the look-alikes faster than color alone.
What minerals are found with hydroxycalcioroméite?+
Hydroxycalcioroméite commonly co-occurs with Mica, Cinnabar, Tripuhyite. Spotting any of these in float or country rock is a useful trip signal.
What kind of rock does hydroxycalcioroméite form in?+
Where it forms: In eluvial sands (Tripuhy, Brazil). Working float back to the host body is the standard way to chase a fresh occurrence.
What is hydroxycalcioroméite used for?+
Hydroxycalcioroméite is used in collector.

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