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Strengite

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Hagendorf South Pegmatite (Cornelia Mine; Hagendorf South Open Cut), Hagendorf, Waidhaus, Vohenstrauß, Oberpfälzer Wald, Upper Palatinate, Bavaria, Germany
© Stephan Wolfsried

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Formula:
FePO
 
4
 · 2H
 
2
O
System:OrthorhombicColour:Purple, violet, pink, ...
Hardness:3½ - 4
Member of:Variscite Group
Name:Named after Johann August Streng (1830-1897), Professor of Mineralogy, University of Giessen, Germany.


Variscite-Strengite Series.

Classification of Strengite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:7/C.09-60
Nickel-Strunz 10th (pending) edition ID:8.CD.10

8 : PHOSPHATES, ARSENATES, VANADATES
C : Phosphates without additional anions, with H2O
D : With only medium-sized cations, RO4:H2O = 1:2
Dana 8th edition ID:40.4.1.2

40 : HYDRATED NORMAL PHOSPHATES,ARSENATES AND VANADATES
4 : (AB)5(XO4)2·xH2O
Hey's CIM Ref.:19.13.2

19 : Phosphates
13 : Phosphates of Fe alone
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Type Occurrence of Strengite

Type Locality:Eleonore Mine, Rodheim-Bieber, Wetzlar, Hesse, Germany
Year of Discovery:1877

Occurrences of Strengite

Geological Setting:Secondary mineral formed under surface or near-surface conditions by the alteration of iron-bearing phosphates, such as Triphylite in pegmatite, or Dufrenite, or may occur in limonite ore deposits and gossans, magnetite iron ores, or rarely as a cave mineral.

Physical Properties of Strengite

Lustre:Vitreous
Diaphaneity (Transparency):Transparent, Translucent
Colour:Purple, violet, pink, peach-blossom-red, carmine, greenish white, colorless; Colourless to pale pink in transmitted light.
Streak:white
Hardness (Mohs):3½ - 4
Cleavage:Distinct/Good
Good on {010}, poor on {001}
Density (measured):2.84 - 2.87 g/cm3
Density (calculated):2.84 g/cm3

Crystallography of Strengite

Crystal System:Orthorhombic
Class (H-M):mmm (2/m 2/m 2/m) - Dipyramidal
Space Group:Pbca {P21/b 21/c 21/a}
Cell Parameters:a = 8.7233(7) Å, b = 9.886(1) Å, c = 10.122(1) Å
Ratio:a:b:c = 0.882 : 1 : 1.024
Unit Cell Volume:V 872.91 ų
Z:8
Morphology:Crystals octahedral {111}; thick to thin tabular {001}; stout prismatic [100] or [010]. May be lathlike, radial fibrous, botyroidal or spherical aggregates and crusts.
Twinning:Rarely on {201}
Crystal Atlas:
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Strengite no.1 - Goldschmidt (1913-1926)
Strengite no.3 - Goldschmidt (1913-1926)

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Optical Data of Strengite

Type:Biaxial (+)
RI values: nα = 1.697 - 1.708 nβ = 1.708 - 1.719 nγ = 1.741 - 1.745
2V:Calculated: 72° to 88°
Maximum Birefringence:δ = 0.044

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:High
Dispersion:relatively strong r < v

Chemical Properties of Strengite

Formula:
FePO
 
4
 · 2H
 
2
O
Essential elements:Fe, H, O, P
All elements listed in formula:Fe, H, O, P
Common Impurities:Al

Relationship of Strengite to other Species

Series:Forms a series with Variscite (see here)
Forms a series with Scorodite (see here)
Member of:Variscite Group
Other Members of Group:

- +
Mansfieldite
AlAsO
 
4
 · 2H
 
2
O
Scorodite
FeAsO
 
4
 · 2H
 
2
O
Variscite
AlPO
 
4
 · 2H
 
2
O
Yanomamite
InAsO
 
4
 · 2H
 
2
O
Common Associates:
VivianiteRockbridgeitePhosphosideriteLimoniteFrondelite
DufréniteCacoxeniteBerauniteApatite
Related Minerals - Nickel-Strunz Grouping):

- +
8.CD.05Kolbeckite
ScPO
 
4
 · 2H
 
2
O
8.CD.05Metavariscite
AlPO
 
4
 · 2H
 
2
O
8.CD.05Phosphosiderite
FePO
 
4
 · 2H
 
2
O
8.CD.05UM2005-02-AsO:AlHPScSi
ScAsO
 
4
 · 2H
 
2
O
8.CD.10Mansfieldite
AlAsO
 
4
 · 2H
 
2
O
8.CD.10Scorodite
FeAsO
 
4
 · 2H
 
2
O
8.CD.10Variscite
AlPO
 
4
 · 2H
 
2
O
8.CD.10Yanomamite
InAsO
 
4
 · 2H
 
2
O
8.CD.15Parascorodite
FeAsO
 
4
 · 2H
 
2
O
8.CD.20Ludlamite
(Fe,Mn,Mg)
 
3
(PO
 
4
)
 
2
 · 4H
 
2
O
8.CD.25Sterlinghillite
Mn
 
3
(AsO
 
4
)
 
2
 · 4H
 
2
O
8.CD.30Rollandite
Cu
 
3
(AsO
 
4
)
 
2
 · 4H
 
2
O
Related Minerals - Hey's Index Grouping:

- +
19.13.1Barbosalite
Fe
2+
 
Fe
3+
2
(PO
 
4
)
 
2
(OH)
 
2
19.13.3Phosphosiderite
FePO
 
4
 · 2H
 
2
O
19.13.4Dufrénite
Ca
 
0.5
Fe
2+
 
Fe
3+
5
(PO
 
4
)
 
4
(OH)
 
6
 · 2H
 
2
O
19.13.5Giniite
Fe
2+
 
Fe
3+
4
(PO
 
4
)
 
3
(OH)
 
5
 · 2H
 
2
O
19.13.6Whitmoreite
Fe
2+
 
Fe
3+
2
(PO
 
4
)
 
2
(OH)
 
2
 · 4H
 
2
O
19.13.7Tinticite
Fe
3+
5.34
(PO
 
4
)
 
3.62
(VO
 
4
)
 
0.38
(OH)
 
4
 · 6.7H
 
2
O
19.13.8Ferristrunzite
Fe
3+
 
Fe
3+
2
(PO
 
4
)
 
2
(OH)
 
3
 · 5H
 
2
O
19.13.9Ferrostrunzite
Fe
2+
 
Fe
3+
2
(PO
 
4
)
 
2
(OH)
 
2
 · 6H
 
2
O
19.13.10Beraunite
Fe
2+
 
Fe
3+
5
(PO
 
4
)
 
4
(OH)
 
5
 · 4H
 
2
O
19.13.11Vivianite
Fe
2+
3
(PO
 
4
)
 
2
 · 8H
 
2
O
19.13.12Metavivianite
Fe
2+
 
Fe
3+
2
(PO
 
4
)
 
2
(OH)
 
2
 · 6H
 
2
O

Other Names for Strengite

Other Languages:
German:Strengit
Russian:Штренгит
Spanish:Strengita
Varieties:
Aluminian Strengite

Other Information

Other Information:Soluble in HCl but not in HNO3.
Health Warning:No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Strengite

Reference List:

- +
Zepharovich (1867) Konigliche Akademie der Wissenschaften, Vienna, Sitzber.: 56: 20 (as Barrandite).

Nies (1877) Neues Jahrbuch für Mineralogie, Geologie und Paleontologie, Heidelberg, Stuttgart: 8-16.

Schaller, Waldemar Theodore (1913), The refractive indices of strengite: Journal of the Washington Academy of Science: 3: 249.

Laubmann and Steinmetz (1920) Zeitschrift für Kristallographie, Mineralogie und Petrographie, Leipzig: 55: 542-546.

Goldschmidt, V. (1922) Atlas der Krystallformen. 9 volumes, atlas, and text: vol. 8: 89.

de Jesus (1935) Com. Serv. Geol. Portugal: 19: 65.

Himmel and Schroeder (1935) Zentralblatt Mineralien: 289.

Kokkoros (1938) Prakt. Ac. Athénes: 13: 337 (Min. Abs. (1941): 8: 140).

McConnell (1940) American Mineralogist: 25: 719.

Palache, C., Berman, H., & Frondel, C. (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, Yale University 1837-1892, Volume II. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged, 1124 pp.: 756-761.

Anthony, J.W., Bideaux, R.A., Bladh, K.W., and Nichols, M.C. (2000) Handbook of Mineralogy, Volume IV. Arsenates, Phosphates, Vanadates. Mineral Data Publishing, Tucson, AZ, 680pp.: 567.

Song, Y., Zavalij, P. Y., Suzuki, M. & Whittingham, M. S. (2002): New iron(III) phosphate phases: crystal structure and electrochemical and magnetic properties. Inorganic Chemistry 41, 5778-5786.

Taxer, K. and Bartl, H. (2004): On the dimorphy between the variscite and clinovariscite group: refined finestructural relationship of strengite and clinostrengite, Fe(PO4) • 2H2O. Crystal Research and Technology 39, 1080-1088.

Internet Links for Strengite

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    • Localities for Strengite

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    Locality Updated: Jenkins Hillemory Quarry (Richardson; Timertone; Emery; Rosemite Cement; Yosemite Cement), Clearing House, Clearing House District, East Belt, Mariposa Co., California, USAFrom Chester S. Lemanski, Jr., 18th May 2013 16:47:46