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Systematic Micaceous Minerals

Saturday, 29 December 2012 09:00 PM

Not all micaceous looking minerals fall in the MICA group of phyllosilicate minerals. Many of the other silicates appear micaceous but are not. We'll have a look at some of these minerals and hopefully explain the difference. Take a look at our article on Mica and Other Micaceous Minerals.

Muscovite

with Pyrite - #PD34674
Locality
Lengenbach quarry, Binn Valley, Wallis, Switzerland 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
7 x 5 x 3 cm - Sm Cabinet 

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Dioctahderal.

This locality demonstrates the diversity in which Muscovite occurs. At Lengenbach, hydrothermal mineralization of base metals occured in Triassic dolostones in which at least 130 minerals (Mindat) have been identified. Muscovite being just incidental to tht overall selection of rare sulfides and sulfosalts.

On this piece, Muscovite crystals occur as slightly pale green platy crystals.


Muscovite

Formula
KAl2(Si3Al)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Massive - Lamellar, Foliated, Micaceous 
Cleavage
Perfect, None, None 
Luster
Vitreous (Glassy) 
Color
white, gray, silver white, brownish white, greenish white 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Brittle - Sectile 
Hardness
2-2.5 
Collection
Phillips Collection
Mineralpedia
View Muscovite
On Dakota Matrix
Previously Sold Muscovite
On Dakota Matrix
Other Available Muscovite
WebMineral
View Muscovite
Mindat
View Muscovite
SOLD
Muscovite - PD34684
Muscovite - PD34684

Muscovite

#PD34684
Locality
Franklin, Sussex Co., New Jersey, United States 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
11 x 6 x 1.5 cm - Cabinet 

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Dioctahderal.

Large dep brown foliated plate of Muscovite, although this one could easily be Hendricksite of a Biotite.


Muscovite

Formula
KAl2(Si3Al)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Massive - Lamellar, Foliated, Micaceous 
Cleavage
Perfect, None, None 
Luster
Vitreous (Glassy) 
Color
white, gray, silver white, brownish white, greenish white 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Brittle - Sectile 
Hardness
2-2.5 
Collection
Phillips Collection
Mineralpedia
View Muscovite
On Dakota Matrix
Previously Sold Muscovite
On Dakota Matrix
Other Available Muscovite
WebMineral
View Muscovite
Mindat
View Muscovite

Muscovite

var. fuchsite - #PD34688
Locality
Kola Peninsula, Russia 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
10 x 5.5 x 3.5 cm - Cabinet 

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Dioctahderal. Fuchsite is nothing but a chromium mica containing up to 4.8% Cr2O3 (encycl. of Min.) imparting the green color and was originally described from Schwarzenstein in the Zillerthal and named after J. N. von Fuchs (Dana 6th Ed.).

This specimen contains nice blades of deep blue Kyanite.


Muscovite

Formula
KAl2(Si3Al)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Massive - Lamellar, Foliated, Micaceous 
Cleavage
Perfect, None, None 
Luster
Vitreous (Glassy) 
Color
white, gray, silver white, brownish white, greenish white 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Brittle - Sectile 
Hardness
2-2.5 
Collection
Phillips Collection
Mineralpedia
View Muscovite
On Dakota Matrix
Previously Sold Muscovite
On Dakota Matrix
Other Available Muscovite
WebMineral
View Muscovite
Mindat
View Muscovite

Muscovite

#PD34689
Locality
Warren Brothers quarry, Bristol Co., Massachusetts, United States 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
10 x 7 x 3 cm - Cabinet 

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Dioctahderal.

This specimen contains hundreds of pseudohexagonal platy crystals to 7-10mm.


Muscovite

Formula
KAl2(Si3Al)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Massive - Lamellar, Foliated, Micaceous 
Cleavage
Perfect, None, None 
Luster
Vitreous (Glassy) 
Color
white, gray, silver white, brownish white, greenish white 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Brittle - Sectile 
Hardness
2-2.5 
Collection
Phillips Collection
Mineralpedia
View Muscovite
On Dakota Matrix
Previously Sold Muscovite
On Dakota Matrix
Other Available Muscovite
WebMineral
View Muscovite
Mindat
View Muscovite

Muscovite

"ballpeen" habit - #PD34690
Locality
Branchville, Fairfield Co., Connecticut, United States 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
10 x 9 x 3 cm - Cabinet 

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Dioctahderal.

An excellent example of "ball-peen" muscovite.


Muscovite

Formula
KAl2(Si3Al)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Massive - Lamellar, Foliated, Micaceous 
Cleavage
Perfect, None, None 
Luster
Vitreous (Glassy) 
Color
white, gray, silver white, brownish white, greenish white 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Brittle - Sectile 
Hardness
2-2.5 
Collection
Phillips Collection
Mineralpedia
View Muscovite
On Dakota Matrix
Previously Sold Muscovite
On Dakota Matrix
Other Available Muscovite
WebMineral
View Muscovite
Mindat
View Muscovite

Muscovite

"ruby mica" - #PD34693
Locality
Walden Gem quarry, Portland, Middlesex Co., Connecticut, United States 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
8 x 7 x 6 cm - Sm Cabinet 

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Dioctahderal. You might call Muscovite the generic mica or the original mica to which all subsequent micas were modelled after. Maybe that's complete bologne, but looking at the formula and crystal chemistry it is straight forward and serves a basis to compare all other micas.

This specimen may contain Rb, which causes the "ruby" color.


Muscovite

Formula
KAl2(Si3Al)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Massive - Lamellar, Foliated, Micaceous 
Cleavage
Perfect, None, None 
Luster
Vitreous (Glassy) 
Color
white, gray, silver white, brownish white, greenish white 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Brittle - Sectile 
Hardness
2-2.5 
Collection
Phillips Collection
Mineralpedia
View Muscovite
On Dakota Matrix
Previously Sold Muscovite
On Dakota Matrix
Other Available Muscovite
WebMineral
View Muscovite
Mindat
View Muscovite

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