Jahnsite-(CaMnMg) Mineral Data

Jahnsite-(CaMnMg) Mineral Data +

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General Jahnsite-(CaMnMg) Information

Chemical Formula:

CaMnMg2Fe+++2(PO4)4(OH)2·8(H2O)

Composition:

Molecular Weight = 813.34 gm

Calcium 4.93 % Ca 6.89 % CaO

Magnesium 5.98 % Mg 9.91 % MgO

Manganese 6.75 % Mn 8.72 % MnO

Iron 13.73 % Fe 19.63 % Fe₂O₃

Phosphorus 15.23 % P 34.90 % P₂O₅

Hydrogen 2.23 % H 19.93 % H₂O

Oxygen 51.15 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

CaMn²⁺Mg₂Fe³⁺₂(PO₄)₄(OH)₂·8(H₂O)

IMA Status:

Approved IMA 1974

Locality:

Tip Top pegmatite, Custer, South Dakota, USA. Link to MinDat.org Location Data.

Name Origin:

Named for Richard H. Jahns (1915-1983), mineralogist and pegmatite expert, Stanford University, Palo Alto, California, USA.

Synonym:

Jahnsite

Jahnsite-(CaMnMg) Image

Images:

Jahnsite-(CaMnMg)

Comments: Brown, striated, transparent crystals of jahnsite-(CaMnMg) on matrix.
Location: Tip Top mine, Custer, Custer County, South Dakota, USA. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Jahnsite-(CaMnMg) Crystallography

Axial Ratios:

a:b:c =2.0924:1:1.3907

Cell Dimensions:

a = 14.94, b = 7.14, c = 9.93, Z = 2; beta = 110.68° V = 991.00 Den(Calc)= 2.73

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: P 2/a

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 9.27(1), 2.825(0.8), 4.91(0.6),

Crystal Structure:

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Moore P B , Araki T , American Mineralogist , 59 (1974) p.964-973, Jahnsite, CaMnMg2(H2O)8Fe2(OH)2[PO4]4: A novel stereoisomerism of, ligands about octahedral corner-chains

Physical Properties of Jahnsite-(CaMnMg)

Cleavage:

[001] Good

Color:

Brown, Purplish brown, Yellow, Yellow orange, Greenish yellow.

Density:

2.706 - 2.718, Average = 2.71

Diaphaniety:

Transparent to Translucent

Fracture:

Brittle - Generally displayed by glasses and most non-metallic minerals.

Hardness:

4 - Fluorite

Luster:

Vitreous - Adamantine

Streak:

white

Optical Properties of Jahnsite-(CaMnMg)

Gladstone-Dale:

CI meas= 0.013 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.019 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2403,KPDmeas= 0.2419,KC= 0.245

Optical Data:

Biaxial (+), a=1.64, b=1.658, g=1.67, bire=0.0300

Pleochroism (x):

pale purple.

Pleochroism (y):

deep purplish brown.

Pleochroism (z):

greenish yellow.

Calculated Properties of Jahnsite-(CaMnMg)

Electron Density:

r_electron=2.71 gm/cc
note: r_{Jahnsite-(CaMnMg)}=2.71 gm/cc.

Fermion Index

Fermion Index = 0.0092
Boson Index = 0.9908

Photoelectric:

PE_{Jahnsite-(CaMnMg)}= 7.19 barns/electron
U=PE_{Jahnsite-(CaMnMg)} x r_electron= 19.50 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Jahnsite-(CaMnMg) is Not Radioactive

Jahnsite-(CaMnMg) Classification

Dana Class:

42.11.2.1 (42)Hydrated Phosphates, etc., Containing Hydroxyl or Halogen

(42.11)where (AB)4 (XO4)3 Zq · x(H2O)

(42.11.2)Dana Group

42.11.2.1 Jahnsite-(CaMnMg) CaMnMg2Fe2(PO4)4(OH)2·8(H2O) P 2/a 2/m

42.11.2.2 Jahnsite-(CaMnFe) CaMnFe2Fe2(PO4)4(OH)2·8(H2O) P 2/a 2/m

42.11.2.3 Jahnsite-(CaMnMn) CaMnMn2Fe2(PO4)4(OH)2·8(H2O) P 2/a 2/m

42.11.2.4 Jahnsite-(MnMnMn)* MnMnMn2Fe2(PO4)4(OH)2·8(H2O) P 2/a 2/m

Strunz Class:

VII/D.29-50 VII - Phosphates, Arsenates and Vanadates

VII/D - Water-bearing phosphates with unfamiliar anions, cations of very big and medium size: Al, Mg and Ca, Na, K

VII/D.29 - Whiteite - Jahnsite group

VII/D.29-10 Whiteite-(CaFeMg) Ca(Fe,Mn)Mg2Al2(PO4)4(OH)2·8(H2O) P 2₁/a 2/m

VII/D.29-20 Whiteite-(CaMnMg) CaMnMg2Al2(PO4)4(OH)2·8(H2O) P 2/a 2/m

VII/D.29-30 Whiteite-(MnFeMg) (Mn,Ca)(Fe,Mn)Mg2Al2(PO4)4(OH)2·8(H2O) P 2/a 2/m

VII/D.29-40 Rittmannite MnMnFeAl2(OH)2(PO4)4·8(H2O) P 2/a 2/m

VII/D.29-50 Jahnsite-(CaMnMg) CaMnMg2Fe2(PO4)4(OH)2·8(H2O) P 2/a 2/m

VII/D.29-60 Jahnsite-(CaMnFe) CaMnFe2Fe2(PO4)4(OH)2·8(H2O) P 2/a 2/m

VII/D.29-70 Jahnsite-(CaMnMn) CaMnMn2Fe2(PO4)4(OH)2·8(H2O) P 2/a 2/m

VII/D.29-75 Jahnsite-(MnMnMn)* MnMnMn2Fe2(PO4)4(OH)2·8(H2O) P 2/a 2/m

VII/D.29-80 Keckite Ca(Mn,Zn)2Fe3(PO4)4(OH)3·2(H2O) P 2₁/a 2/m

Other Jahnsite-(CaMnMg) Information

References:

NAME( Dana8) PHYS. PROP.(Dana8) OPTIC PROP.(Dana8)

See Also:

Links to other databases for Jahnsite-(CaMnMg) :
1 -Am. Min. Crystal Structure Database 2 -Athena 3 -Google Images 4 -Google Scholar 5 -MinDAT 6 -MinMax(Deutsch) 7 -MinMax(English) 8 -Mineralienatlas (Deutsch) 9 -QUT Mineral Atlas 10 - WWW-MINCRYST

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Print or Cut-and-Paste your Jahnsite-(CaMnMg) Specimen Label here :

Jahnsite-(CaMnMg)

CaMnMg2Fe+++2(PO4)4(OH)2·8(H2O)
Dana No: 42.11.2.1 Strunz No: VII/D.29-50
Locality:

Notes: