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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

var. fuchsite - #BM43856
Locality
Minas Gerais, Brazil 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
11 x 6 x 4 cm - Cabinet 

Light but rich green chromium Muscovite called fuchsite.


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

var. gilbertite - #PD30953
Locality
Gunheath China Clay Pit, St. Austell, Cornwall, England 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
8 x 6.5 x 4.5 cm - Sm Cabinet 

This is a variety of Muscovite usually fine-grained. 


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

Paragonite

#46474
Locality
Slyudorudnik mine, Kyshtym, Chelyabinsk Oblast', Urals, Russia 
Formula
NaAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
4 x 2.5 x 1.5 cm - Miniature 
Special Info
XRD Confirmed 
Special Info
EDS Confirmed 

Light green flashy micaceous plates of Paragonite, positively identified by Dr. Igor Pekov.


Paragonite

Formula
NaAl2(Si3Al)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Scaly, Massive - Fibrous 
Cleavage
Perfect, None, None 
Luster
Pearly 
Color
white, yellow 
Streak
white 
Class
Monoclinic 
Hardness
2.5 
Special Info
XRD Confirmed
Special Info
EDS Confirmed
SOLD
Paragonite - PD46716
Paragonite - PD46716

Paragonite

#PD46716
Locality
Slyudorudnik mine, Kyshtym, Chelyabinsk Oblast', Urals, Russia 
Formula
NaAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
2 x 1 x 1 cm - Thumbnail 

Light green plates of micaceous Paragonite, and sodium mica.


Paragonite

Formula
NaAl2(Si3Al)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Scaly, Massive - Fibrous 
Cleavage
Perfect, None, None 
Luster
Pearly 
Color
white, yellow 
Streak
white 
Class
Monoclinic 
Hardness
2.5 
Collection
Phillips Collection

Phlogopite

#PD46683
Locality
Otter Lake, Quebec, Canada 
Formula
KMg3(Si3Al)O10(OH)2 
Availability
Sold
Size
8 x 5 x 5 cm - Sm Cabinet 

Dark almost black mass of Phlogopite mica.

Phyllosilicate - Monoclinic - Mica group member. Phologpite is classified as an Ordinary (True or Common) Mica - Trioctahderal with Mg at the (M) positions, K as (I), and OH as (A). Mg end member of Biotite-Phlogopite series.

Occurs sometimes as primary mineral in igneous rocks, mainly ultrabasic, in Leucite-pyroxene rock called "Wyomingite", serpentenized dunnites, altered kimberlites, alkaline ultrabasic rocks in Kola, Russia.


Phlogopite

Formula
KMg3(Si3Al)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Micaceous, Scaly, Lamellar 
Cleavage
Perfect, None, None 
Luster
Vitreous - Pearly 
Color
brown, gray, green, yellow, reddish brown 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Uneven 
Hardness
2-2.5 
Collection
Phillips Collection
SOLD
POLYLITHIONITE - PD32104
POLYLITHIONITE - PD32104

Polylithionite

on Epistolite - #PD32104
Locality
Kangerdluarssuq, Ilimaussaq, Greenland 
Formula
KLi2AlSi4O10F2 
Availability
Sold
Size
5 x 3 x 3 cm - Miniature 

Polylithionite is a lithium bearing mica. The specimen shows a nice face of cleavable mica with a nice green color. It is an excellent example.


Polylithionite

Formula
KLi2AlSi4O10F2 
Crystal System
Monoclinic 
Crystal Habit
Pseudo Hexagonal, Tabular, Scaly 
Cleavage
Perfect, None, None 
Luster
Pearly 
Color
bluish, colorless, violet, greenish, pearl white 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Uneven 
Hardness
2-3 
Collection
Phillips Collection

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