Koragoite Mineral Data

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General Koragoite Information

Chemical Formula:

(Mn++,Fe+++)3(Nb,Ta,Ti)2(Nb,Mn)2(W,Ta)2O20

Composition:

Molecular Weight = 1,241.59 gm

Tantalum 16.03 % Ta 19.57 % Ta₂O₅

Titanium 1.16 % Ti 1.93 % TiO₂

Manganese 13.50 % Mn 12.86 % MnO / 5.09 % Mn₂O₃

Niobium 17.96 % Nb 25.69 % Nb₂O₅

Iron 3.37 % Fe 4.82 % Fe₂O₃

Tungsten 22.21 % W 28.01 % WO₃

Oxygen 25.77 % O

______ ______

100.00 % 97.97 % = TOTAL OXIDE

Empirical Formula:

Mn²⁺_2.25Fe³⁺_0.75Nb_1.2Ta_0.6Ti_0.3Nb_1.2Mn³⁺_0.8W_1.5Ta_0.5O₂₀

Environment:

In granitic pegmatites.

IMA Status:

Approved IMA 1995

Locality:

Vez-Dara River valley, Shakhdara Range, in the southwestern Pamir Mountains, Tajikistan. Link to MinDat.org Location Data.

Name Origin:

Named after Aleksei Aleksandrovich Korago (1942–1993), geologist who investigated the formation of river pearls in the Arkhangel'sk district of Russia, and the origin of amber.

Name Pronunciation:

Koragoite + Pronunciation

Synonym:

IMA1994-049

Koragoite Image

Images:

Koragoite

Comments: Black tabular crystals of koragoite in matrix.
Location: Vez-Dara River Valley, Shakhdara Range, Khorog Region, Gorno-Badakhshan District, Pamir Mts, Tajikistan. Scale: Picture size 1.8 mm.
© Thomas Witzke / Abraxas-Verlag

Koragoite Crystallography

Axial Ratios:

a:b:c =4.8912:1:1.1392

Cell Dimensions:

a = 24.73, b = 5.056, c = 5.76, Z = 2; beta = 103.5° V = 700.30 Den(Calc)= 5.89

Crystal System:

Monoclinic - SphenoidalH-M Symbol (2) Space Group: P 2₁

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

By Intensity(I/I_o): 2.98(1), 3.69(0.8), 3.74(0.8),

Crystal Structure:

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Yamnova N A , Pushcharovskii D Yu , Voloshin A V , Kristallografiya , 40 (1995) p.469-475, Crystal structure of a new natural Mn, W-tantaloniobate

Physical Properties of Koragoite

Cleavage:

None

Color:

Red, Brownish red.

Density:

4.7 - 6.22, Average = 5.46

Diaphaneity:

Opaque

Fracture:

Brittle - Uneven - Very brittle fracture producing uneven fragments.

Habit:

Platy - Sheet forms (e.g. micas).

Hardness:

4-5 - Fluorite-Apatite

Luster:

Metallic

Streak:

grayish brown

Optical Properties of Koragoite

Optical Data:

NCalc= 2.24 - from Gladstone-Dale relationship (KC = 0.2097) where Ncalc=Dcalc*KC+1
NCalc= 2.15 - from Gladstone-Dale relationship (KC = 0.2097) where Ncalc=Dmeas*KC+1

RL Anisotrophism:

Weak.

RL Bireflectance:

Weak.

RL Color:

Light gray.

RL Pleochroism:

None.

Reflectivity

**Standardized Intensity (100%) Reflection Spectra of Koragoite in Air**
λ	R₁	R₂	∑ R₁(λ)	∑ R₂(λ)
470 nm	19.20	18.00
546 nm	18.50	17.50
589 nm	19.30	18.50
650 nm	16.50	16.00

**Calculated Relative Intensity Colors of Koragoite in Air**
Relative Intensity	0%	60%	100%	120%	180%	240%	300%	360%	420%	480%	510%
R₁
R₂

Calculated Properties of Koragoite

Electron Density:

Bulk Density (Electron Density)=5.24 gm/cc
note: Specific Gravity of Koragoite =5.89 gm/cc.

Fermion Index:

Fermion Index = 0.03
Boson Index = 0.97

Photoelectric:

PE_Koragoite= 488.76 barns/electron
U=PE_Koragoite x rElectron Density=2,560.01 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Koragoite is Not Radioactive

Koragoite Classification

Dana Class:

08.07.12.01 (08)Multiple Oxides with Nb, Ta, and Ti

(08.07)Dana Type

(08.07.12)Dana Group

08.07.12.01 Koragoite (Mn,Fe)3(Nb,Ta,Ti)2(Nb,Mn)2(W,Ta)2O20 P 2₁ 2

Strunz Class:

04.DE.10 04 - OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodate

04.D - Metal:Oxygen = 1:2 and similar

04.DE -With medium-sized cations; with various polyhedra

04.DE.10 Koragoite (Mn,Fe)3(Nb,Ta,Ti)2(Nb,Mn)2(W,Ta)2O20 P 2₁ 2

Other Koragoite Information

References:

NAME( MinRec) PHYS. PROP.(Am.Min.,Vol.81,1996) OPTIC PROP.(MinRec, v 29, p 473)

See Also:

Links to other databases for Koragoite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - Google Images
4 - Google Scholar
5 - Handbook of Mineralogy (UofA)
6 - MinDAT
7 - MinMax(Deutsch)
8 - MinMax(English)
9 - Mineralienatlas (Deutsch)
10 - QUT Mineral Atlas
11 - Ruff.Info
12 - WWW-MINCRYST

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Print or Cut-and-Paste your Koragoite Specimen Label here :

Koragoite

(Mn++,Fe+++)3(Nb,Ta,Ti)2(Nb,Mn)2(W,Ta)2O20
Dana No: 08.07.12.01 Strunz No: 04.DE.10
Locality:

Notes: