Macfallite (original) (raw)

A valid IMA mineral species

About MacfalliteHide

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Formula:

Ca2Mn3+3(SiO4)(Si2O7)(OH)3

Mn may be replaced by minor Al.

Colour:

Reddish-brown, maroon, dull pink

Lustre:

Sub-Adamantine, Silky

Crystal System:

Monoclinic

Name:

Named in 1979 by Paul (Paulus) Brian Moore, Jun Ito, and Ian M. Steele in honor of Russell Patterson MacFall [1 September 1903 Indianapolis, Indiana, USA - 6 September 1983 Coronado, California, USA] editor for Chicago Tribune newspaper and, earlier, for other newspapers. Russ was an amateur mineralogist interested in systematic mineralogy and an author of six books on popular mineralogy, paleontology, and geology. Russ was also a specialist in the minerals of the region where macfallite was first discovered.

This page provides mineralogical data about Macfallite.

Unique IdentifiersHide

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Long-form identifier:

mindat:1:1:2508:5

8ceeebbe-2136-4a15-861d-310a3fea6b20

IMA Classification of MacfalliteHide

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Type description reference:

Classification of MacfalliteHide

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9.BG.15

9 : SILICATES (Germanates)
B : Sorosilicates
G : Sorosilicates with mixed SiO4 and Si2O7 groups; cations in octahedral [6] and greater coordination

58.2.3.2

58 : SOROSILICATES Insular, Mixed, Single, and Larger Tetrahedral Groups
2 : Insular, Mixed, Single, and Larger Tetrahedral Groups with cations in [6] and higher coordination; single and double groups (n = 1, 2)

16.16.20

16 : Silicates Containing Aluminum and other Metals
16 : Aluminosilicates of Mn

Mineral SymbolsHide

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As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

Physical Properties of MacfalliteHide

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Transparency:

Transparent, Translucent

Colour:

Reddish-brown, maroon, dull pink

Streak:

Brown with a reddish tint

Density:

3.43(2) g/cm3 (Measured) 3.53 g/cm3 (Calculated)

Optical Data of MacfalliteHide

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RI values:

_n_α = 1.773 - 1.775 _n_β = 1.795 _n_γ = 1.810 - 1.815

2V:

Measured: 86° , Calculated: 78° to 88°

δ = 0.037 - 0.040

Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.

Comments:

X = colorless to yellow; Y = light brown; Z = dark brown to reddish brown.

Comments:

2V(meas.) = Very large

Chemistry of MacfalliteHide

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Mindat Formula:

Ca2Mn3+3(SiO4)(Si2O7)(OH)3

Mn may be replaced by minor Al.

Common Impurities:

Ti,Al,Fe,Cr,V,Cu,Mg,K,Na,H2O

Crystallography of MacfalliteHide

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Crystal System:

Monoclinic

Class (H-M):

2/m - Prismatic

Cell Parameters:

a = 10.235(3) Å, b = 6.086(6) Å, c = 8.970(5) Å
β = 110.75(3)°

Ratio:

a:b:c = 1.682 : 1 : 1.474

Unit Cell V:

522.50 ų (Calculated from Unit Cell)

Twinning:

By reflection on {100}, commonly repeated.

Crystal StructureHide

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ID	Species	Reference	Link	Year	Locality	Pressure (GPa)	Temp (K)
0000966	Macfallite	Moore P B, Shen J, Araki T (1985) Crystal chemistry of the (M2)3+ phi2 sheet: Structural principles and crystal structures of ruizite, macfallite and orientite American Mineralogist 70 171-181		1985	Lake Manganese, Copper Harbor, Keweenaw County, Michigan, USA	0	293
0004767	Macfallite	Nagashima M, Rahmoun N S, Alekseev E V, Geiger C A, Armbruster T, Akasaka M (2008) Crystal chemistry of macfallite: Relationships to sursassite and pumpellyite American Mineralogist 93 1851-1857		2008	Manganese Lake, Copper Harbor, Keweenaw County, Michigan	0	293

CIF Raw Data - click here to close

X-Ray Powder DiffractionHide

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Powder Diffraction Data:

Geological EnvironmentHide

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Type Occurrence of MacfalliteHide

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General Appearance of Type Material:

radial and framboidal aggregates

Place of Conservation of Type Material:

National Museum of Natural History, Washington, D.C., USA, 135923; The Natural History Museum, London, England, 1984,139.

Associated Minerals at Type Locality:

Reference:

Moore, P.B., Ito, J., and Steele, I.M. (1979) Macfallite and orientite: calcium manganese (III) silicates from upper Michigan. Mineralogical Magazine: 43: 325-331.

Synonyms of MacfalliteHide

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Other Language Names for MacfalliteHide

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Common AssociatesHide

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Associated Minerals Based on Photo Data:

Related Minerals - Strunz-mindat GroupingHide

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Other InformationHide

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Health Risks:

No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

Internet Links for MacfalliteHide

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References for MacfalliteHide

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Localities for MacfalliteHide

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This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

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