Where it forms, where it's found
- Geological setting
Phosphatic laterite; weathered phosphorite.
- Type locality
- Clay Canyon
- Fairfield
- Sunshine Mining District
- Utah County
- Utah
- USA
40.2764°, -112.1604°
14recorded occurrences
Physical
Optical
- Optical type
- Biaxial (+)
- Refractive index
- 1.584 – 1.602
- Surface relief
- Moderate
- Principal indices
- nα 1.584 · nβ 1.598 · nγ 1.602
- Dispersion
- small
Δ = 0Δmax
PPLpleochroism per grain
XPLindependent extinctions · rotate the stage
PPLpleochroism only · colour blends on rotation
XPLinterference colour · extinct every 90°
Retardation180 nm
Order1st order
XPL colour
Crystallography
- Cell parameters
- a = 7.00 Å · c = 18.99 Å
- Z
- 2
- Morphology
Chalcedonic crusts or spherules with a fine-fibrous structure.
- Comment
Other values reported: 7.00, 19.07 (Owens et al., 1960).
Chemical composition
Synonyms
- Millisiet
- Pallite
In other languages
- German
- Millisit
- Italian
- Millisite
Classification
Strunz
10th ed.8.DL.10
- 8Phosphates, Arsenates, VanadatesClass
- 8.DPhosphates, etc. with additional anions, with H2ODivision
- 8.DLWith large and medium-sized cations, (OH, etc.):RO4 = 2:1Group
- 8.DL.10MillisiteSpecies
Dana
8th ed.42.07.09.01
- 42Hydrated Phosphates, Etc.containing Hydroxyl or HalogenClass
- 42.07(AB)2(XO4)Zq·xH2OType
- 42.07.09— unnamed intermediate level —Group
- 42.07.09.01MillisiteSpecies
CIM
—19.8.20
- 19PhosphatesClass
- 19.8Phosphates of Al and other metalsGroup
- 19.8.20MillisiteSpecies
Group, growth & confusion
Literature, links & citation
Citations
- 1930Larsen, Esper S., Shannon, Earl V. (1930) The minerals of the phosphate nodules from near Fairfield, Utah. American Mineralogist, 15 (8) 307-337
- 1942Larsen, Esper S., 3d, (1942) The mineralogy and paragenesis of the variscite nodules from near Fairfield, Utah, Part 1. American Mineralogist, 27 (4) 281-300
- 1951Palache, Charles; Berman, Harry; Frondel, Clifford (1951) The System of Mineralogy (7th ed.) Vol. 2 - Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. John Wiley and Sons.
- 1960Owens, J.P., Altschuler, Z.S., Berman, R. (1960) Millisite in phosphorite from Homeland, Florida. American Mineralogist: 45: 547-561.
- 1970Fanfani, L., Nunzi, A., Zanazzi, P. F. (1970) The crystal structure of wardite. Mineralogical Magazine, 37 (289) 598-605 doi:10.1180/minmag.1970.037.289.10 DOI: 10.1180/minmag.1970.037.289.10
Cite this entry
@misc{mineral2026,
author = {Mineral Index editorial board},
title = {Millisite — Mineral Index},
year = {2026},
url = {https://mineralindex.org/minerals/millisite-2712},
note = {Accessed 2026-05-11}
}