Mineral Information and Data:

Jimthompsonite
Mg5Si6O16(OH)2 [CNMNC approved formula]

Named for James Burleigh Thompson, Jr. (1921- ), eminent petrologist of Harvard University, Cambridge, Massachusetts, USA.

IMA status : Approved Species 1978 (IMA1977-011)
CLASSIFICATION 
Dana
(8th edition) :
67.01.01.01  
  (67) Inosilicate Unbranched Chains with W>2
  (67.01) with W=3
  (67.01.01) Jimthompsonite group
  
Nickel-Strunz
(10th edition) :
09.DF.05
  (09) Silicates
  (09.D) Inosilicates* Structural terminology per Liebau (1985)
  (09.DF) with 2-periodic multiple chains
  
Crystal system: Orthorhombic System
Point group (H-M): mmm (or 2/m 2/m 2/m) — dipyramidal
Space group: Pbca
Unit cell: a = 18.6263(3) Å, b = 27.2303(6) Å, c = 5.2970(3) Å, Z=8
Crystal Habit: As radiating sprays of crystals, to 5 cm; as fibrous intergrowths parallel to {010} in anthophyllite and cummingtonite.
  
Color: Colorless to very light pinkish brown; colorless in thin section
Diaphaneity: Transparent
Cleavage: Perfect on {210}, intersecting at 38° and 142°; breakage on {100} and {010} may be partings
  
Polymorphism and Series: Dimorphous with clinojimthompsonite.
Geologic Setting: In the black wallrock between chlorite and actinolite zones of a metamorphosed ultramafic body.
Mineral Association: Chesterite, clinojimthompsonite, anthophyllite, cummingtonite, talc
  

 

Jimthompsonite
Pale green to white glassy crystalline fibrous clinojimthompsonite intergrown with jimthompsonite.
Origin: Chester, Windsor County, Vermont, USA.
Photo: Jeff Weissman

<<< BACK TO MINERAL SEARCH