RockHoundR

Fluorcalciomicrolite is a complex tantalate mineral belonging to the pyrochlore supergroup. It typically appears as small, octahedral crystals in highly evolved granitic pegmatites and is prized by collectors for its radioactive chemistry and rare occurrence.

Hardness
4-5
Mohs
Luster
Adamantine to resinous
Streak
White
Transparency
Translucent

Is this fluorcalciomicrolite?

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 fluorcalciomicrolite with a known reference. Fluorcalciomicrolite 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: adamantine to resinous.
  • 4
    Match the color range
    Compare against the expected color range: colorless.
  • 5
    Look at form & habit
    Crystal system: cubic. Typical habit: octahedral crystals.

Often confused with

Fluorcalciomicrolite 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 Fluorcalciomicrolite leaves white, Pyrochlore leaves brown; luster reads adamantine to resinous on Fluorcalciomicrolite and vitreous to resinous on Pyrochlore.

Compare →

Often found alongside fluorcalciomicrolite

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

All properties

Chemical formula
(Ca,Na)₂Ta₂O₆F
Mohs hardness
4-5
Density
6.160 g/cm³
Colors
Colorless
Streak
White
Luster
Adamantine to resinous
Transparency
Translucent
Crystal system
Cubic
Crystal habit
Octahedral crystals
Cleavage
None
Rarity
Rare
Uses
Collector, Scientific study
Host rock
In heavy mineral concentrates from a rare-element granitic pegmatite exceptionally enriched in lithium and rubidium

Where rockhounds find fluorcalciomicrolite

Classic worldwide localities

  • Harding pegmatite, New Mexico, USA
  • Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil

Field-hunting tip

Where it forms: In heavy mineral concentrates from a rare-element granitic pegmatite exceptionally enriched in lithium and rubidium. If you start seeing microcline, albite, quartz 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 fluorcalciomicrolite?+
Mohs hardness is 4-5. Luster: adamantine to resinous. The streak is white. Common colors include colorless.
Where is fluorcalciomicrolite found?+
Notable localities include Harding pegmatite, New Mexico, USA; Volta Grande pegmatite, Nazareno, Minas Gerais, Brazil.
Is fluorcalciomicrolite safe to handle?+
Fluorcalciomicrolite contains trace uranium or thorium. Contains thorium and uranium which make it radioactive; handle with care and wash hands after contact.
What rocks look like fluorcalciomicrolite?+
Fluorcalciomicrolite 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 fluorcalciomicrolite?+
Fluorcalciomicrolite commonly co-occurs with Microcline, Albite, Quartz, Muscovite, Spodumene, Lepidolite. Spotting any of these in float or country rock is a useful trip signal.
What kind of rock does fluorcalciomicrolite form in?+
Where it forms: In heavy mineral concentrates from a rare-element granitic pegmatite exceptionally enriched in lithium and rubidium. Working float back to the host body is the standard way to chase a fresh occurrence.
What is fluorcalciomicrolite used for?+
Fluorcalciomicrolite is used in collector, scientific study.

Find fluorcalciomicrolite on the map

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

Download on the App StoreGet it on Google Play