Fluorstrophite

Where it forms, where it's found

Geological setting: Alkalic pegmatites
Type locality: Inagli chrome diopside deposit
Inagli Massif
Aldan
Sakha
Russia
58.5367°, 124.9140°

9recorded occurrences

Source · OpenStreetMap

Physical

Hardness: 1Talc
2Gypsum
3Calcite
4Fluorite
5Apatite
6Orthoclase
7Quartz
8Topaz
9Corundum
10Diamond
Transparency: Transparent · Translucent
Colour: Green to yellow-green · colourless

Optical

Optical type: Uniaxial (-)
Refractive index: 1.637 – 1.651
Surface relief: Moderate
Principal indices: n_ω 1.651 · n_ε 1.637

Michel-Lévy diagramhighlighted lineδ = 0.0140

Attainable Michel-Lévy rangeΔ ∈ [0, t·δ_max]140 nm1st order

Δ = 0Δ_max

Section thickness10 μmStage rotation0°

Thin-section mosaic70 grains · random 3D orientations

PPL

pleochroism per grain

XPL

independent extinctions · rotate the stage

Interference simulatorsingle grain · PPL ↔ XPL

PPL

pleochroism only · colour blends on rotation

XPL

interference colour · extinct every 90°

Retardation140 nm

Order1st order

XPL colour

Crystallography

Crystal system: Hexagonal
Space group: #108
Cell parameters: a = 9.565(8) Å · c = 7.115(3) Å
Z: 2
Morphology: Crystals short to long hexagonal prisms [0001], with (1010) and (1011) dominant; also thick tabular (0001), frequently in the crystals of hydrothermal origin in pegmatites and veins, with (1010), relatively large (0001), and often also (1011) or low pyramids. Massive, coarse granular to compact.
Type-locality form: Poorly formed oval crystals 0.2x1 cm in longitudinal section and as small crystals with corroded faces.
Comment: Space group P63/m or P63.

Crystal structure

Chemical composition

Constituent elements: Mass composition breakdown
Element Atoms At. mass g/mol Mass g/mol Mass share
38SrStrontium Strontium 4 87.620 350.480
50.47%
8OOxygen Oxygen 12 15.999 191.988
27.64%
15PPhosphorus Phosphorus 3 30.974 92.922
13.38%
20CaCalcium Calcium 1 40.078 40.078
5.77%
9FFluorine Fluorine 1 18.998 18.998
2.74%
Total 694.466 100.00%
Mass share = atoms × atomic mass ÷ molar mass × 100
From IMA formula

Mass composition breakdown
Element	Atoms	At. mass g/mol	Mass g/mol	Mass share
38SrStrontium	Strontium	4	87.620	350.480	50.47%
8OOxygen	Oxygen	12	15.999	191.988	27.64%
15PPhosphorus	Phosphorus	3	30.974	92.922	13.38%
20CaCalcium	Calcium	1	40.078	40.078	5.77%
9FFluorine	Fluorine	1	18.998	18.998	2.74%
	Total	694.466	100.00%

Synonyms

Apatite-(SrOH)
Fluorstrophiet
Strontiapatit
Strontiapatita
Strontium-Apatite (of Efimov et al.)

In other languages

German: Fluorstrophit
Italian: Apatite-(SrOH) · Fluorstrophite · Stronzio-apatite

Classification

Strunz

10th ed.

8.BN.05

8Phosphates, Arsenates, VanadatesClass
8.BPhosphates, etc., with additional anions, without H₂ODivision
8.BNWith only large cations, (OH, etc.):RO₄ = 0.33:1Group
8.BN.05FluorstrophiteSpecies

Dana

8th ed.

41.08.01.07

41Anhydrous Phosphates, Etc.containing Hydroxyl or HalogenClass
41.08A₅(XO₄)₃Z_qType
41.08.01Apatite GroupGroup
41.08.01.07FluorstrophiteSpecies

CIM

—

22.1.18

22Phosphates, Arsenates or Vanadates with other AnionsClass
22.1Phosphates, arsenates or vanadates with fluorideGroup
22.1.18FluorstrophiteSpecies

Group, growth & confusion

6 members

Literature, links & citation

Citations

—Kristallografiya: 32: 891-895.
1939Volkova and Melentiev (1939) Comptes rendus de l’académie des sciences de l’U.R.S.S., n.s.: 25: 120.
1962Fleischer, Michael; Foster, Margaret D. (1962) New mineral names. American Mineralogist, 47 (5-6). 805-812
1962Efimov, A.F., Kravchenko, S.M., Vasil’eva, Z.V. (1962) Strontium-apatite — a new mineral. Doklady Akademii Nauk SSSR: 142: 439-442.
1964Klevtsova, R.F. (1964) The crystal structure of strontium-apatite. Journal of Structural Chemistry: 5: 318-320.

Cite this entry

@misc{mineral2026,
  author    = {Mineral Index editorial board},
  title     = {Fluorstrophite — Mineral Index},
  year      = {2026},
  url       = {https://mineralindex.org/minerals/fluorstrophite-3757},
  note      = {Accessed 2026-05-11}
}