Oxyphlogopite is a rare member of the mica group characterized by the substitution of hydroxyl ions by oxygen, typically resulting from oxidation in high-temperature volcanic environments. It is physically similar to common phlogopite but can often be distinguished by its deeper reddish-brown hues and specific geological occurrence within volcanic ejecta.

Hardness

2.5-3

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrarePhlogopite family

Oxyphlogopite

Hardness: 2.5-3
Luster: Pearly
Streak: White
Transparency: Translucent

No image

Is this oxyphlogopite?

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 oxyphlogopite with a known reference. Oxyphlogopite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Oxyphlogopite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Oxyphlogopite typically shows a pearly luster.
4
Match the color range
Compare against the expected color range: brown, reddish-brown, dark-brown.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals, scaly aggregates, disseminated flakes.

Often confused with

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

Often found alongside oxyphlogopite

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

All properties

Chemical formula: K(Mg,Fe³⁺)₃(AlSi₃O₁₀)(OH,O)₂
Mohs hardness: 2.5-3
Density: 2.8-3.0 g/cm³
Colors: Brown Reddish-brown Dark-brown
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Tabular Crystals, Scaly Aggregates, Disseminated Flakes
Cleavage: Perfect Basal
Rarity: Rare
Uses: Collector, Scientific Research
Host rock: Alkaline Igneous Rocks, Carbonatites
Typical price: $20-100 per specimen

Where rockhounds find oxyphlogopite

Classic worldwide localities

Monte Somma, Italy
Khibiny Massif, Russia
Kola Peninsula, Russia

Field-hunting tip

Look in alkaline igneous rocks, carbonatites country, the host setting where oxyphlogopite typically forms. If you start seeing sanidine, nepheline, leucite in float, you are in the right ground. Field specimens usually show a tabular crystals, scaly aggregates, disseminated flakes habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify oxyphlogopite?+

Mohs hardness is 2.5-3. It typically shows a pearly luster. The streak is white. Common colors include brown, reddish-brown, dark-brown.

Where is oxyphlogopite found?+

Notable localities include Monte Somma, Italy; Khibiny Massif, Russia; Kola Peninsula, Russia.

How much is oxyphlogopite worth?+

Typical asking prices fall in the range of $20-100 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like oxyphlogopite?+

Oxyphlogopite is most often confused with Phlogopite, Biotite, Annite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with oxyphlogopite?+

Oxyphlogopite commonly co-occurs with Sanidine, Nepheline, Leucite, Augite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does oxyphlogopite form in?+

Oxyphlogopite typically forms in alkaline igneous rocks, carbonatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is oxyphlogopite used for?+

Oxyphlogopite is used in collector, scientific research.

Find oxyphlogopite on the map

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