Phlogopite
Phlogopite is a silicate mineral prized by collectors for its exceptional color range, with several world-class Chinese localities.
About Phlogopite
Phlogopite is classified as a silicate mineral in the mica group (biotite group — trioctahedral mica) and has the chemical formula KMg3(AlSi3O10)(OH)2. It crystallizes in the monoclinic system and is one of the most visually varied minerals in the collector market. Its combination of structural character and global distribution make it a recognized species in both systematic and aesthetic collections.
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.