Phlogopite

Crystal system · Monoclinic

Phlogopite is a silicate mineral prized by collectors for its exceptional color range, with several world-class Chinese localities.

About Phlogopiteextended article

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Crystal Structure
Mg-mica end-member.
External databases provide CIF (Crystallographic Information File) downloads + interactive 3D viewers. AMCSD: American Mineralogist Crystal Structure Database (free, RRUFF-hosted). COD: open community-curated database.
Elemental Composition (by mass)
ElementMass %Visual
O Oxygen41.53%
Si Silicon21.87%
Mg Magnesium18.93%
K Potassium10.15%
Al Aluminum7.00%
H Hydrogen0.52%
Computed from simplified end-member formula. Solid-solution series, water content, and trace substitutions cause real-world variation.
IMA Abbreviation (Whitney-Evans 2010)
Phl
→ Phlogopite
Mg-mica
Standard symbol from American Mineralogist (Whitney & Evans, 2010). Used in thin-section labeling, phase diagrams, and IMA-style species records.
Pronunciation
/ˈflɒɡəpaɪt/
FLOG-uh-pite
Greek "like fire"
Mohs 2–2.5
Vickers (~) 75 HV
Knoop (~) 85 HK
Geological setting
KimberliteMetamorphicSedimentary
Element composition by mass

Formula: KMg₃(AlSi₃O₁₀)(OH,F)₂ · molar mass: 419.25 g/mol

O 41.98%
Si 20.1%
Mg 17.39%
K 9.33%
Al 6.44%
F 4.53%
H 0.24%

Computed from atomic weights (IUPAC 2021). Site-occupancy groups (Fe,Mn) split equally.

GroupMica Group
Related members: Muscovite · Biotite · Lepidolite
Mohs Hardness 2–2.5

Phlogopite sits at 2–2.5 on the Mohs scale — soft enough to be scratched by a fingernail.

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Colors:
Streak
White
Crystal system
Monoclinic
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SilicatesSilicates (Phyllosilicates — Micas)
TL;DR · 1 min read
Phlogopite (KMg₃(AlSi₃O₁₀)(OH,F)₂) is the magnesium end-member of the biotite series and the distinctive bronze-yellow to brown mica. It forms in metamorphosed dolomitic limestones and ultramafic rocks, often as large transparent honey-colored books.
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Phlogopite (KMg₃(AlSi₃O₁₀)(OH,F)₂) is the magnesium end-member of the biotite series and the distinctive bronze-yellow to brown mica. It forms in metamorphosed dolomitic limestones and ultramafic rocks, often as large transparent honey-colored books. Mg-rich phlogopite is a refractory mineral that survives in mantle xenoliths and kimberlite pipes.

More minerals to explore #

Other Members of the Mica Group

云母族

Identification & care

Specimens usually show tabular pseudo-hexagonal crystals; lamellar, scaly, foliated books; six-sided plates. Its color range is broad, including yellowish brown, greenish brown, reddish brown, bronze-brown, pale yellow to colorless, pale green (chromian), and rarely violet. The luster is vitreous, pearly, the streak is white to very pale yellowish, and specimens range from transparent to translucent. The cleavage is perfect basal on {001} — flexible elastic sheets. The fracture is micaceous (cleavage dominant), which aids identification.

Collector context

How it forms

Phlogopite forms in metamorphosed ultramafic rocks (serpentinites, dunites — as a secondary mineral replacing olivine); contact-metamorphic marbles and calc-silicates; kimberlites and lamproites (as a primary magmatic mineral); carbonatites. It is commonly found in association with diopside, tremolite, calcite, dolomite, chrysotile, chlorite, olivine, apatite.

Classic Chinese localities

Documented Chinese occurrences are recorded at Shangbao Mine, Xianghualing Sn-polymetallic ore field and Lingxiang Mine, among others.

Why collectors care

Collectors pursue Phlogopite for the clarity of its crystal form and, in good material, saturated color that reads instantly across a display case. A well-terminated phlogopite on clean matrix photographs well, identifies quickly, and anchors a cabinet piece. Top Chinese specimens over the last two decades have reset the bar for what phlogopite looks like at collector grade.

What affects value

Value in Phlogopite is assessed, in typical order of weight, against: (1) locality provenance; (2) size relative to the species norm; (3) crystal form and termination sharpness; (4) color saturation and zoning; (5) transparency and internal clarity; (6) matrix quality and aesthetic balance; (7) condition (absence of damage, chips, or repair). Cleaning quality and verified locality documentation act as multipliers across the above.

Naming history

The name Phlogopite has a specific etymological and historical context — see Mindat's reference entry for provenance details. We have retained naming data at the record level; published prose is paraphrased from factual fields rather than copied from source.