Fluckite

Fluckite

Fluckite from the Gabe-Gottes Mine
General
Category Arsenate minerals
Formula
(repeating unit)
CaMnH2(AsO4)2·2(H2O) [1]
Strunz classification 08.CB.15
Crystal symmetry Triclinic pinacoidal
H-M symbol: (1)
Space group: P1
Unit cell a = 8.459 Å, b = 7.613 Å, c = 6.968 Å, α = 82.21°, β = 98.25°, γ = 95.86°; Z=2
Identification
Color Colorless, Light to Dark Pink
Crystal habit Crystals prismatic, typically radiating to spherulitic
Crystal system Triclinic
Cleavage (010) perfect, (100) good, (101) indistinct
Mohs scale hardness 3.5-4
Luster Subvitreous, waxy
Streak White
Diaphaneity Translucent
Specific gravity 3.05
Optical properties Biaxial (+), probable
Refractive index nα = 1.618 nβ = 1.627 nγ= 1.642
Birefringence 0.024
2V angle Large
References [1][2][3][4]

Fluckite is an arsenate mineral with the chemical formula CaMnH2(AsO4)2·2(H2O).[1]

Fluckite's mineral crystallography is triclinic meaning it has three axis of different length and three different interior angles that do not equal 90°. Because fluckite possesses three axes with different angles and lengths it is an anisotropic mineral. This means that it has more than one optic axis. This mineral is a member of the P1 space group meaning that it can be rotated 360° degrees and inverted to obtain the original figure. Optically, this mineral has positive biaxial birefringence, which can be shown obtaining an interference figure that is blue in the upper right and lower left quadrants of the figure while looking down the c- axis. Fluckite possesses moderate optical relief which is the degree to which the mineral stands out from the mounting medium.[1]

Occurrence

Fluckite was first described in 1980 for an occurrence in the Gabe-Gottes Mine in Haut-Rhin, Alsace, France,[1][5] and named for mineralogist Pierre Fluck of Louis Pasteur University in Strasbourg, France.[2] The mineral was found in at a depth of 100 m. It occurs as a post-mine phase on carbonate gangue.[5] It occurs in association with native arsenic, tennantite, skutterudite, sainfeldite, pharmacolite, villyaellenite, picropharmacolite, calcite, dolomite, ankerite and quartz.[4]

References

  1. 1 2 3 4 5 Fluckite: mindat.org
  2. 1 2 Fluckite: webmineral.com
  3. Fluckite: Mineral Atlas
  4. 1 2 Fluckite: Handbook of Mineralogy
  5. 1 2 M. Fleischer, L.J. Cabri, G.Y. Chao, and A. Pabst (1980) New Mineral Names*, American Mineralogist, 65,1065-1070.
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