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Micaceous Minerals 2

Monday, 10 April 2017 08:00 AM

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 Quartz - #37784
Locality
Badu Hill pegmatite, Llano Llano Co., Texas, United States 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
6 x 5 x 4 cm - Sm Cabinet 
Tagged
pegmatite mineral  

Very interesting 8mm "books" of Muscovite covering feldspar with a Quartz crystal at the center.


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
Art Smith Collection
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Muscovite

var. alurgite - #BM40736
Locality
Ouro Preto, Minas Gerais, Brazil 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
4 x 2 x 1.5 cm - Miniature 

Alurgite is a variety of Muscovite with manganese impurity giving it the beautiful red 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
McConlogue Collection
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Muscovite

var. fuchsite - #41239
Locality
Bahia, Brazil 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
11.5 x 8 x 2.5 cm - Cabinet 

This specimen is a large cabinet specimen with rich flashy green color exhibiting wavy foliations. It is a much richer green than appears in the photo.

Fuchsite is nothing but a Muscovite mica containing up to 4.8% chromiun (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.).

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


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 
Mineralpedia
View Muscovite
On Dakota Matrix
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On Dakota Matrix
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Muscovite

var. Star (twinned) - #43740
Locality
Jenipapo dist., Itinga, Minas Gerais, Brazil 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
7 x 4.5 x 4 cm - Sm Cabinet 

Twinned Muscovite crystals in star-shaped crystals to 2cm.


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 
Mineralpedia
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On Dakota Matrix
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On Dakota Matrix
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SOLD
Muscovite - 46688
Muscovite - 46688

Muscovite

#46688
Locality
Diamond Mica mine, Pennington Co., South Dakota, United States 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
8 x 5 x 0.3 cm - Sm Cabinet 
Tagged
pegmatite mineral  

A diamond shaped, natural crystal.


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 
Mineralpedia
View Muscovite
On Dakota Matrix
Previously Sold Muscovite
On Dakota Matrix
Other Available Muscovite
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Mindat
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Muscovite

var. phengite - #PD46691
Locality
Dora Maira Massif, Cuneo prov., Piedmont, Italy 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
5.5 x 4 x 2 cm - Sm Cabinet 

Phengite is supposedly a high silica mica. It is a fine grained 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
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Mindat
View Muscovite

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