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Jimthompsonite

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James B. Thompson, Jr.
Formula:
(Mg,Fe)5Si6O16(OH)2
Colour:
colorless to very light pinkish brown
Lustre:
Vitreous, Sub-Vitreous
Hardness:
6 - 7
Specific Gravity:
3.05 (Calculated)
Crystal System:
Orthorhombic
Name:
Named by David R. Veblen and Charles W. Burnham in 1978 in honor of James (Jim) B. Thompson, jr., [November 20, 1921 Calais, Maine, USA - November 15, 2011, Calais, Maine, USA], mineralogist and petrologist, late professor/emeritus at Harvard University, USA.
Jimthomsonite occurs as ultra-microscopic intergrowths within other host minerals, generally amphiboles such as anthophyllite or cummingtonite-series minerals. Jimthompsonite is generally not visible to the naked eye, but instead is observable optically or by transmission electron microscopy.


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Classification of JimthompsoniteHide

Approved
Approval Year:
1977
9.DF.05

9 : SILICATES (Germanates)
D : Inosilicates
F : Inosilicates with 2-periodic multiple chains
67.1.1.1

67 : INOSILICATES Unbranched Chains with W > 2
1 : Unbranched Chains with W>2 with W=3
14.21.11

14 : Silicates not Containing Aluminum
21 : Silicates of Fe and Mg

Physical Properties of JimthompsoniteHide

Vitreous, Sub-Vitreous
Transparency:
Transparent
Colour:
colorless to very light pinkish brown
Streak:
Colorless
Hardness:
6 - 7 on Mohs scale
Hardness Data:
Estimated
Comment:
Undetermined; presumably similar to amphibole.
Tenacity:
Brittle
Cleavage:
Perfect
{210}
Fracture:
Splintery
Density:
3.05 g/cm3 (Calculated)

Optical Data of JimthompsoniteHide

Type:
Biaxial (-)
RI values:
nα = 1.605 nβ = 1.626 nγ = 1.633
2V:
Measured: 62° , Calculated: 58°
Birefringence:
0.028
Max Birefringence:
δ = 0.028
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
r > v weak
Optical Extinction:
Parallel. XYZ = abc
Pleochroism:
Non-pleochroic

Chemical Properties of JimthompsoniteHide

Formula:
(Mg,Fe)5Si6O16(OH)2
IMA Formula:
Mg5Si6O16(OH)2
Common Impurities:
Al,Mn,Ca,Na,H2O

Crystallography of JimthompsoniteHide

Crystal System:
Orthorhombic
Class (H-M):
mmm (2/m 2/m 2/m) - Dipyramidal
Space Group:
Pbca
Setting:
Pbca
Cell Parameters:
a = 18.626 Å, b = 27.23 Å, c = 5.297 Å
Ratio:
a:b:c = 0.684 : 1 : 0.195
Unit Cell V:
2,686.56 ų (Calculated from Unit Cell)
Z:
8
Morphology:
Fibrous intergrowths in host crystals to 5 cm

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
13.6 (60)
8.81 (100)
3.81 (30)
3.25 (40)
3.09 (50)
2.74 (30)
2.60 (40)
2.55 (30)
Comments:
ICDD 31-638 (calculated)

Type Occurrence of JimthompsoniteHide

General Appearance of Type Material:
Occurs as fibrous crystals or microscopic intergrowths parallel to (010) in anthophyllite and cummingtonite.
Geological Setting of Type Material:
Found in the blackwall zone of a metamorphosed ultramafic body
Associated Minerals at Type Locality:

Synonyms of JimthompsoniteHide

Other Language Names for JimthompsoniteHide

Simplified Chinese:镁川石

Common AssociatesHide

Associated Minerals Based on Photo Data:
Clinojimthompsonite2 photos of Jimthompsonite associated with Clinojimthompsonite on mindat.org.
Chesterite2 photos of Jimthompsonite associated with Chesterite on mindat.org.
Talc1 photo of Jimthompsonite associated with Talc on mindat.org.
Anthophyllite1 photo of Jimthompsonite associated with Anthophyllite on mindat.org.

Related Minerals - Nickel-Strunz GroupingHide

9.DF.05Chesterite(Mg,Fe)17Si20O54(OH)6Orth.
9.DF.05Clinojimthompsonite(Mg,Fe)5Si6O16(OH)2Mon.
9.DF.15ErshoviteNa4K3(Fe,Mn,Ti)2Si8O22(OH)4 · 4H2OTric.
9.DF.15ParaershoviteNa3K3Fe3+2Si8O20(OH)4 · 4H2OTric. 1 : P1
9.DF.20Tvedalite(Ca,Mn)4Be3Si6O17(OH)4 · 3H2OOrth.
9.DF.25BaveniteCa4Be2Al2Si9O26(OH)2Orth. mm2
9.DF.30BigcreekiteBaSi2O5 · 4H2OOrth. mmm (2/m 2/m 2/m) : Pnma

Related Minerals - Dana Grouping (8th Ed.)Hide

67.1.1.2Clinojimthompsonite(Mg,Fe)5Si6O16(OH)2Mon.

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

14.21.1Olivine(Mg,Fe2+)2SiO4Orth.
14.21.2Ringwoodite(Mg,Fe2+)2SiO4Iso. m3m (4/m 3 2/m) : Ia3d
14.21.3Wadsleyite(Mg,Fe2+)2(SiO4)Orth.
14.21.4ClinoferrosiliteFe2+SiO3Mon.
14.21.5Anthophyllite☐{Mg2}{Mg5}(Si8O22)(OH)2Orth. mmm (2/m 2/m 2/m) : Pnma
14.21.6Cummingtonite☐{Mg2}{Mg5}(Si8O22)(OH)2Mon.
14.21.7 Magnesiocummingtonite☐{Mg2}{Mg5}(Si8O22)(OH)2
14.21.8Grunerite☐{Fe2+2}{Fe2+5}(Si8O22)(OH)2Mon. 2/m : B2/m
14.21.9MinnesotaiteFe2+3Si4O10(OH)2Tric. 1 : P1
14.21.10Chesterite(Mg,Fe)17Si20O54(OH)6Orth.
14.21.12Clinojimthompsonite(Mg,Fe)5Si6O16(OH)2Mon.
14.21.13MajoriteMg3(Fe2+,Si,Al)2(SiO4)3Iso.
14.21.14Balangeroite(Mg,Fe2+,Fe3+,Mn2+)42Si16O54(OH)40Mon.

Fluorescence of JimthompsoniteHide

Not fluorescent

Other InformationHide

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

References for JimthompsoniteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
American Mineralogist (1978): 63: 1000-1009, 1053-1073.

Internet Links for JimthompsoniteHide

Localities for JimthompsoniteHide

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

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
Finland
 
  • Southwestern Finland Region
    • Salo
      • Kisko
Schumacher, J. & Czank, M. 1987. Mineralogy of triple- and double-chain pyriboles from Orijärvi, southwest Finland. The American Mineralogist 72 (3-4), 345-352.
Greenland
 
  • Sermersooq
    • Nuuk (Godthåb)
http://epsc.wustl.edu/admin/whatsnew/photo_album/week/pw2006-12-06.htm
Italy
 
  • Piedmont
    • Verbano-Cusio-Ossola Province
      • Ossola Valley
        • Antrona Valley
          • Montescheno
Piccoli, G.C., Maletto, G., Bosio, P., Lombardo, B. (2007): Minerali del Piemonte e della Valle d'Aosta. Associazione Amici del Museo "F. Eusebio" Alba, Ed., Alba (Cuneo) 607 pp.
Japan
 
  • Honshu Island
    • Tohoku Region
      • Iwate Prefecture
        • Kitakami Mts
Konishi et al (1991) Koubutsu-Gakkai Kou'en-Youshi, 101.
Switzerland
 
  • Ticino (Tessin)
    • Maggia Valley
      • Lavizzara Valley
        • Fusio
Stalder, H. A., Wagner, A., Graeser, S. and Stuker, P. (1998): "Mineralienlexikon der Schweiz", Wepf (Basel), p. 229-230.
Stalder, H. A., Wagner, A., Graeser, S. and Stuker, P. (1998): "Mineralienlexikon der Schweiz", Wepf (Basel), p. 229-230.
    • Verzasca Valley
Stalder, H. A., Wagner, A., Graeser, S. and Stuker, P. (1998): "Mineralienlexikon der Schweiz", Wepf (Basel), p. 229.
UK
 
  • Scotland
    • North West Highlands
Droop, G.T.R. (1994) Triple-chain pyriboles in Lewisian ultramafic rocks. Mineralogical Magazine, 58, 11, 1-20.
USA (TL)
 
  • Vermont
    • Windsor Co.
      • Chester
AmMin 63:1000
Mineral and/or Locality  
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