Hydroxycalciomicrolite is a rare member of the pyrochlore supergroup typically found as small, distinct octahedral crystals within granitic pegmatites. It is often yellowish to brownish in color and is notable for its radioactivity, which may require specific storage considerations for collectors.

Hardness

5-5.5

Mohs

Luster

Vitreous

Streak

Pale Yellow

Transparency

Translucent

mineralrarePyrochlore Supergroup family

Hydroxycalciomicrolite

Hardness: 5-5.5
Luster: Vitreous
Streak: Pale Yellow
Transparency: Translucent

Is this hydroxycalciomicrolite?

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 hydroxycalciomicrolite with a known reference. Hydroxycalciomicrolite sits at Mohs 5-5.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Hydroxycalciomicrolite leaves a pale yellow streak.
3
Read the luster
Hold the specimen under a strong light. Hydroxycalciomicrolite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, brown, pale yellow.
5
Look at form & habit
Crystal system: cubic. Typical habit: octahedral crystals.

Often found alongside hydroxycalciomicrolite

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

All properties

Chemical formula: (Ca,◻)₂Ta₂O₆(OH)
Mohs hardness: 5-5.5
Density: 4.5-5.0 g/cm³
Colors: Yellow Brown Pale Yellow
Streak: Pale Yellow
Luster: Vitreous
Transparency: Translucent
Crystal system: Cubic
Crystal habit: Octahedral Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Granite Pegmatites
Typical price: $50-300 per specimen

Where rockhounds find hydroxycalciomicrolite

Classic worldwide localities

Finland
Sweden
Brazil

Field-hunting tip

Look in granite pegmatites country — that is the host setting where hydroxycalciomicrolite typically forms. If you start seeing albite, quartz, lepidolite in float, you are in the right ground. Field specimens usually show a octahedral crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify hydroxycalciomicrolite?+

Mohs hardness is 5-5.5. It typically shows a vitreous luster. The streak is pale yellow. Common colors include yellow, brown, pale yellow.

Where is hydroxycalciomicrolite found?+

Notable localities include Finland; Sweden; Brazil.

How much is hydroxycalciomicrolite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is hydroxycalciomicrolite safe to handle?+

This mineral is radioactive. Contains radioactive elements (typically U or Th impurities); handle with care and wash hands thoroughly after handling. Store away from other minerals to prevent cross-contamination. Handle with care, avoid grinding or breathing dust, and store separately.

What minerals are found with hydroxycalciomicrolite?+

Hydroxycalciomicrolite commonly co-occurs with Albite, Quartz, Lepidolite, Tourmaline. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does hydroxycalciomicrolite form in?+

Hydroxycalciomicrolite typically forms in granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is hydroxycalciomicrolite used for?+

Hydroxycalciomicrolite is used in collector.

Find hydroxycalciomicrolite on the map

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