Mineral Information and Data:

Parvowinchite
(Na,Mn4+)(Mg4Fe3+)Si8O22(OH)2 [CNMNC approved formula]

Named for its high content of the small cations Mn and Mg (latin: parvo = small) and its relation to winchite. Previously known as tirodite (IMA discredited, 1997) to be subsequently approved as fluorian manganoan winchite (IMA, 1997). Approved and defined in Group 5, the Na–Ca–Mg–Fe–Mn–Li amphiboles, where BLi ≤ 0.50 apfu per nomenclature of amphiboles (IMA, 2003)

IMA status : Approved Species 2003 (IMA2003-066)
CLASSIFICATION 
Dana
(8th edition) :
66.01.03b.01a  
  (66) Inosilicate Double-Width Unbranched Chains, W=2
  (66.01) with P=2 amphibole configuration
  (66.01.03b) Group 3, the sodic-calcic amphiboles
  
Nickel-Strunz
(10th edition) :
09.DE.20
  (09) Silicates
  (09.D) Inosilicates* Structural terminology per Liebau (1985)
  (09.DE) with 2-periodic double chains, Si4O11; Clinoamphiboles
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 9.704Å, b = 17.99Å, c = 5.297Å, β = 103.51°
Crystal Habit: Tabular-prismatic crystals to 7 cm
  
Color: Straw yellow, pale orange
Diaphaneity: Transparent, Translucent
Luster: Vitreous
Hardness (Mohs): 6.5
Measured Density: 3.12 (calculated) g/cm3
Cleavage: Perfect on {010}
Tenacity: Brittle
Streak: White
  
  
Synonyms/varieties: Tirodite, alkali-bearing manganocummingtonite

 

Parvowinchite
Colorless, transparent turneaureite masses
with light brown parvowinchite and darker brown donpeacorite.
Origin: 2500' level of the mine, ZCA Mine No. 4 (St Joe Mine; ZCA No. 4 mine), Balmat, Balmat-Edwards Zinc District,
St Lawrence Co., New York, USA.
Picture size: 5mm
Photo: Jeff Weissman

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