Fluorotetraferriphlogopite is a rare mica-group mineral occurring primarily in carbonatites and alkaline igneous environments. Collectors identify it by its characteristic platy, micaceous habit and distinctive iron-rich brown coloration typical of the phlogopite-annite series.
Is this fluorotetraferriphlogopite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch fluorotetraferriphlogopite with a known reference. Fluorotetraferriphlogopite sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale brown.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly.
- 4Match the color rangeCompare against the expected color range: brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, micaceous masses.
Often confused with
Fluorotetraferriphlogopite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Fluorotetraferriphlogopite leaves pale brown, Phlogopite leaves white.
How to tell apart: Streak differs, so Fluorotetraferriphlogopite leaves pale brown, Biotite leaves white; luster reads pearly on Fluorotetraferriphlogopite and splendent to submetallic, vitreous, pearly on cleavage on Biotite.
How to tell apart: Streak differs, so Fluorotetraferriphlogopite leaves pale brown, Annite leaves brownish white; luster reads pearly on Fluorotetraferriphlogopite and vitreous on Annite.
Often found alongside fluorotetraferriphlogopite
Minerals reported to co-occur with fluorotetraferriphlogopite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KMg₃FeSi₃O₁₀F₂
- Mohs hardness
- 3-4
- Density
- 2.966 g/cm³
- Colors
- Streak
- Pale brown
- Luster
- Pearly
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Platy crystals, micaceous masses
- Cleavage
- Perfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In metamorphosed carbonate rocks associated with a large REE-Fe-Nb deposit
Where rockhounds find fluorotetraferriphlogopite
Classic worldwide localities
- South ore body, East Mine, Bayan Obo, Inner Mongolia, China
Field-hunting tip
Where it forms: In metamorphosed carbonate rocks associated with a large REE-Fe-Nb deposit. If you start seeing fluorbritholite-, norbergite, richterite in float, you are in the right ground. Typical habit: platy crystals, micaceous masses. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify fluorotetraferriphlogopite?+
Where is fluorotetraferriphlogopite found?+
What rocks look like fluorotetraferriphlogopite?+
What minerals are found with fluorotetraferriphlogopite?+
What kind of rock does fluorotetraferriphlogopite form in?+
What is fluorotetraferriphlogopite used for?+
Find fluorotetraferriphlogopite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
