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Micaceous Minerals

Saturday, 26 February 2022 08:00 AM

Introducing the "Micaceous Minerals" gallery which is part of our Special Edition galleries. This gallery contains mineral specimens for sale including vermiculite, wonesite, zinnwaldite and more from places like Easton Talc quarry, Northampton Co., Pennsylvania, United States, Post Pond Volcanics, Norwich, Windsor Co., Vermont, United States, Ploskaya Mt, Western Keivy Massif, Kola Peninsula, Russia, and Zinnwald, Erzgebirge, Bohemia, Czech Republic.

Vermiculite

#AH54186
Locality
Easton Talc quarry, Northampton Co., Pennsylvania, United States 
Formula
Mg0.7(Mg,Fe3+,Al)6(Si,Al)8O20(OH)4·8H2
Availability
Sold
Size
8 x 6 x 6 cm - Sm Cabinet 

Small to large (4cm), yellow plates of micaceous Vermiculite.

Although a monoclinic phyllosilicate, Vermiculite is not a mica group member. But it  is micaceous. It is a member of the Montmorillonite-Vermiculate group with 2:1 layering, meaning there are two (T) tetrahedral layers with an (M) octahedral layer in between. There is no (I) interlayer and the 2:1 layers are instead held together by weak Van der Waals bonds.

Vermiculate requires Biotite, Chlorite, Hornblend and Serpentines to form. Vermiculite contains so much water it will exfoliate when burned.


Vermiculite

Formula
Mg0.7(Mg,Fe3+,Al)6(Si,Al)8O20(OH)4·8H2
Crystal System
Monoclinic 
Crystal Habit
Lamellar, Scaly 
Cleavage
Perfect, None, None 
Luster
Vitreous - Dull 
Color
colorless, green, gray white, yellow brown 
Streak
greenish white 
Class
Monoclinic - Prismatic 
Fracture
Uneven 
Hardness
1.5-2 
Collection
Arnold G Hampson Collection

Wonesite

#PD48252
Locality
Post Pond Volcanics, Norwich, Windsor Co., Vermont, United States 
Formula
(Na,K,□)(Mg,Fe,Al)6(Si,Al)8O20(OH,F)4 
Availability
Sold
Size
1.3 x 0.5 x 0.2 cm - Thumbnail 
Special Info
Type Locality 

Greenish micaceous small specimen. Wonesite is rather rare and occurs at the Post Pond volcanic rock as epitactic intergrowths with Phlogopite and talc in metamorphosed volcanics (Lauf, RJ - Collector's Guide to the Mica Group).


Wonesite

Formula
(Na,K,[box])(Mg,Fe,Al)6(Si,Al)8O20(OH,F)4 
Crystal System
Monoclinic 
Crystal Habit
Flakes 
Cleavage
Perfect, None, None 
Luster
Vitreous (Glassy) 
Color
yellow brown, dark brown 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Micaceous 
Hardness
2.5-3 
Collection
Don Phillips Collection
Special Info
Type Locality
Mineralpedia
View Wonesite
On Dakota Matrix
Previously Sold Wonesite
On Dakota Matrix
Other Available Wonesite
WebMineral
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Mindat
View Wonesite
SOLD
Zinnwaldite - 46490
Zinnwaldite - 46490

Zinnwaldite

#46490
Locality
Ploskaya Mt, Western Keivy Massif, Kola Peninsula, Russia 
Formula
K(Al,Fe,Li)3(Si,Al)4O10(OH)F 
Availability
Sold
Size
3.5 x 2 x 1.5 cm - Miniature 
Special Info
XRD Confirmed 
Special Info
EDS Confirmed 

Black micaceous Zinnwaldite composing the entire mass. Identified by Dr. Igor Pekov.


Zinnwaldite

Formula
KLiFe++Al(AlSi3)O10(F,OH)2 
Crystal System
Monoclinic 
Crystal Habit
Pseudo Hexagonal, Micaceous, Platy 
Cleavage
Good, None, None 
Luster
Vitreous - Pearly 
Color
light brown, silvery white, gray, yellowish white, greenish white 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Uneven 
Hardness
3.5-4 
Special Info
XRD Confirmed
Special Info
EDS Confirmed

Zinnwaldite

#BW57295
Locality
Zinnwald, Erzgebirge, Bohemia, Czech Republic 
Formula
K(Al,Fe,Li)3(Si,Al)4O10(OH)F 
Availability
Sold
Size
5.5 x 3.5 x 3.5 cm - Sm Cabinet 
Special Info
Type Locality 

Zinnwaldite is a dark brown lithium bearing mica, which has been discredited by the IMA. On this specimen it occurs as golden brown micaceous crystals.

Zinnwaldite is a phyllosilicate, mica group member. It is an Ordinary (True or Common) Mica - Trioctahedral. It is a lithium bearing transitional member on the Siderophyllite-Polylitionite series.


Zinnwaldite

Formula
KLiFe++Al(AlSi3)O10(F,OH)2 
Crystal System
Monoclinic 
Crystal Habit
Pseudo Hexagonal, Micaceous, Platy 
Cleavage
Good, None, None 
Luster
Vitreous - Pearly 
Color
light brown, silvery white, gray, yellowish white, greenish white 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Uneven 
Hardness
3.5-4 
Collection
Bill Wilson Collection
Special Info
Type Locality

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