Oxycalciopyrochlore is a rare member of the pyrochlore group, typically found as small, well-formed octahedral crystals in carbonatite deposits. It is identifiable by its dark brown to black coloration and submetallic to vitreous luster. Due to its radioactive content, it is primarily a specimen of interest for advanced mineral collectors and those studying complex oxide geochemistry.

Hardness

Mohs

Luster

Vitreous

Streak

Pale brown to cream

Transparency

Semitransparent

mineralrarePyrochlore Group family

Oxycalciopyrochlore

Hardness: ~5
Luster: Vitreous
Streak: Pale brown to cream
Transparency: Semitransparent

Is this oxycalciopyrochlore?

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 oxycalciopyrochlore with a known reference. Oxycalciopyrochlore sits at Mohs ~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 brown to cream.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: dark brown, brown-black.
5
Look at form & habit
Crystal system: cubic. Typical habit: octahedral crystals.

Often confused with

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

mineral

Pyrochlore

Mohs 5-5.5

How to tell apart: Streak differs, so Oxycalciopyrochlore leaves pale brown to cream, Pyrochlore leaves brown.

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Often found alongside oxycalciopyrochlore

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

All properties

Chemical formula: Ca₂Nb₂O₆O
Mohs hardness: ~5
Density: 5.30 g/cm³
Colors: Dark brownBrown-black
Streak: Pale brown to cream
Luster: Vitreous
Transparency: Semitransparent
Crystal system: Cubic
Crystal habit: Octahedral crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: As replacement masses and in veinlets, in a granite pegmatite in a serpentinite

Where rockhounds find oxycalciopyrochlore

Classic worldwide localities

Věžná, Czech Republic

Field-hunting tip

Where it forms: As replacement masses and in veinlets, in a granite pegmatite in a serpentinite. If you start seeing columbite, niobian rutile, antimony in float, you are in the right ground. Typical habit: octahedral crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify oxycalciopyrochlore?+

Mohs hardness is ~5. Luster: vitreous. The streak is pale brown to cream. Common colors include dark brown, brown-black.

Where is oxycalciopyrochlore found?+

Notable localities include Věžná, Czech Republic.

Is oxycalciopyrochlore safe to handle?+

Oxycalciopyrochlore contains trace uranium or thorium. Contains thorium and uranium trace elements which render it radioactive; handle with care and store in a sealed container away from living areas.

What rocks look like oxycalciopyrochlore?+

Oxycalciopyrochlore 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 oxycalciopyrochlore?+

Oxycalciopyrochlore commonly co-occurs with Columbite, Niobian rutile, Antimony, Stokesite, Cassiterite, Zircon. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does oxycalciopyrochlore form in?+

Where it forms: As replacement masses and in veinlets, in a granite pegmatite in a serpentinite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is oxycalciopyrochlore used for?+

Oxycalciopyrochlore is used in collector.

Find oxycalciopyrochlore on the map

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