Jacobsite Mineral Data

Jacobsite Mineral Data +

General Jacobsite Information

Chemical Formula:

(Mn++,Fe++,Mg)(Fe+++,Mn+++)2O4

Composition:

Molecular Weight = 227.38 gm

Magnesium 1.07 % Mg 1.77 % MgO

Manganese 26.58 % Mn 18.72 % MnO / 17.36 % Mn₂O₃

Iron 44.21 % Fe 9.48 % FeO / 52.67 % Fe₂O₃

Oxygen 28.15 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Mn²⁺_0.6Fe²⁺_0.3Mg_0.1Fe³⁺_1.5Mn³⁺_0.5O₄

Environment:

A primary mineral or and alteration product of othe rmanganese-bearing minerals in some metamorphosed Mn deposits. Dimorphous with iwakiite and forms a series with magnetite.

IMA Status:

Valid Species (Pre-IMA) 1869

Locality:

Jakobsberg, Sweden. Link to MinDat.org Location Data.

Name Origin:

Named after its locality.

Synonym:

ICSD 28517

PDF 74-2403

Jacobsite Image

Images:

Jacobsite Barite

Comments: Sharp, octahedral crystals of Jacobsite on a bladed barite matrix.
Location: N' Chwaning II Mine, Kuruman, South Africa. Scale: 3x2.5x1.9 cm.
© Isaias Casanova / IC Minerals

Images:

Jacobsite Ganomalite

Comments: White crystalline ganomalite with dark granular jacobsite.
Location: Jacobsberg, Varmland, Sweden. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Jacobsite Crystallography

Cell Dimensions:

a = 8.499, Z = 8; V = 613.91 Den(Calc)= 4.92

Crystal System:

Isometric - HexoctahedralH-M Symbol (4/m 3 2/m) Space Group: F d3m

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

By Intensity(I/I_o): 2.563(1), 1.503(0.4), 3.005(0.35),

Forms:

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Forms: [ 1 1 1]

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Crystal Structure:

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Lucchesi S , Russo U , Della Giusta A , European Journal of Mineralogy , 9 (1997) p.31-42, Crystal chemistry and cation distribution in some, Mn-rich natural and synthetic spinels, Sample: JBS1

View Additional jPOWD Structure files for Jacobsite
[1] [2]

Physical Properties of Jacobsite

Cleavage:

None

Color:

Iron black, Black.

Density:

4.75

Diaphaniety:

Opaque

Fracture:

Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).

Habit:

Disseminated - Occurs in small, distinct particles dispersed in matrix.

Habit:

Massive - Granular - Common texture observed in granite and other igneous rock.

Hardness:

5.5-6 - Knife Blade-Orthoclase

Luster:

Sub Metallic

Magnetism:

Weakly magnetic

Streak:

reddish black

Optical Properties of Jacobsite

Optical Data:

Isotropic, n=2.3.

RL Color:

Grayish with with olive tint and brown internal reflections.

Reflectivity

**Standardized Intensity (100%) Reflection Spectra of Jacobsite in Air**
λ	R	∑ R(λ)
400 nm	19.00
420 nm	18.80
440 nm	18.60
460 nm	18.40
480 nm	18.20
500 nm	18.10
520 nm	18.00
540 nm	17.80
560 nm	17.60
580 nm	17.40
600 nm	17.20
620 nm	17.00
640 nm	16.80
660 nm	16.60
680 nm	16.50
700 nm	16.40

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

Calculated Properties of Jacobsite

Electron Density:

r_electron=4.65 gm/cc
note: r_Jacobsite=4.92 gm/cc.

Fermion Index

Fermion Index = 0.01057
Boson Index = 0.98943

Photoelectric:

PE_Jacobsite= 20.56 barns/electron
U=PE_Jacobsite x r_electron= 95.64 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Jacobsite is Not Radioactive

Jacobsite Classification

Dana Class:

7.2.2.2 (7)Multiple Oxides

(7.2)(A+ B++)2 X4 Spinel group

(7.2.2)(Iron subgroup)

7.2.2.1 Magnesioferrite MgFe2O4 F d3m 4/m 3 2/m

7.2.2.2 Jacobsite (Mn,Fe,Mg)(Fe,Mn)2O4 F d3m 4/m 3 2/m

7.2.2.3 Magnetite FeFe2O4 F d3m 4/m 3 2/m

7.2.2.4 Franklinite (Zn,Mn,Fe)(Fe,Mn)2O4 F d3m 4/m 3 2/m

7.2.2.5 Trevorite NiFe2O4 F d3m 4/m 3 2/m

7.2.2.6 Cuprospinel (Cu,Mg)Fe2O4 F d3m 4/m 3 2/m

7.2.2.7 Brunogeierite (Ge,Fe)Fe2O4 F d3m 4/m 3 2/m

Strunz Class:

IV/B.02-30 IV - Oxides

IV/B - Oxides with metal : oxygen = 3:4 (spinel type M3O4 and related), Ferrite-Spinels

IV/B.02 - Spinel group, Magnesioferrite - Franklinite series

IV/B.02-10 Magnesioferrite MgFe2O4 F d3m 4/m 3 2/m

IV/B.02-20 Magnetite FeFe2O4 F d3m 4/m 3 2/m

IV/B.02-30 Jacobsite (Mn,Fe,Mg)(Fe,Mn)2O4 F d3m 4/m 3 2/m

IV/B.02-40 Trevorite NiFe2O4 F d3m 4/m 3 2/m

IV/B.02-50 Cuprospinel (Cu,Mg)Fe2O4 F d3m 4/m 3 2/m

IV/B.02-60 Franklinite (Zn,Mn,Fe)(Fe,Mn)2O4 F d3m 4/m 3 2/m

Other Jacobsite Information

References:

NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(AntBidBlaNic3)

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

Jacobsite

(Mn++,Fe++,Mg)(Fe+++,Mn+++)2O4
Dana No: 7.2.2.2 Strunz No: IV/B.02-30
Locality:

Notes: