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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.

Masutomilite

#PD34813
Locality
Hirukawa, Gifu Pref., Chubu, Honshu Island, Japan 
Formula
KLiAlMn2+(Si3Al)O10(F,OH)2 
Availability
Sold
Size
Chip < 1cm 

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Trioctahderal. Contains Li, Al, Mn2+ in the (M) octahedral sites with F>OH in the (A) position. Mindat places K & Rb in the Interlayer sites.

Rare worldwide with only in two in the USA, originally described from Japan. According to Bernard & Hyrsl, occurs in Na-Li rich pegmatites in Czech Republic, and Japan and is typically purple to pink.


Masutomilite

Formula
KLiAlMn2+(Si3Al)O10(F,OH)2 
Crystal System
Monoclinic 
Crystal Habit
Pseudo Hexagonal 
Cleavage
Perfect, None, None 
Luster
Vitreous - Pearly 
Color
purple pink 
Streak
white 
Class
Monoclinic - Prismatic 
Hardness
2.5 
Collection
Phillips Collection
SOLD
Masutomilite - PD34814
Masutomilite - PD34814

Masutomilite

#PD34814
Locality
Hirukawa, Gifu Pref., Chubu, Honshu Island, Japan 
Formula
KLiAlMn2+(Si3Al)O10(F,OH)2 
Availability
Sold
Size
3 x 2.5 x 0.1 cm - Thumbnail 

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Trioctahderal. Contains Li, Al, Mn2+ in the (M) octahedral sites with F>OH in the (A) position. Mindat places K & Rb in the Interlayer sites.

Rare worldwide with only in two in the USA, originally described from Japan. According to Bernard & Hyrsl, occurs in Na-Li rich pegmatites in Czech Republic, and Japan and is typically purple to pink.

This is a small cleavage plate.


Masutomilite

Formula
KLiAlMn2+(Si3Al)O10(F,OH)2 
Crystal System
Monoclinic 
Crystal Habit
Pseudo Hexagonal 
Cleavage
Perfect, None, None 
Luster
Vitreous - Pearly 
Color
purple pink 
Streak
white 
Class
Monoclinic - Prismatic 
Hardness
2.5 
Collection
Phillips Collection
SOLD
Montdorite - PD34815
Montdorite - PD34815

Montdorite

#PD34815
Locality
Mont Dore, Charlannes, Auvergne, France 
Formula
KFe2+1.5Mn2+0.5Mg0.5Si4O10(F,OH)2 
Availability
Sold
Size
Capsule 
Special Info
Type Locality 

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Trioctahderal. Mn in the octahedrally coordinated positions and Fluorine in the (A) position.

Per Lauf, occurs as minute 5-25 micron sized green crystals, in aluminum poor micas and was not found in nature until 1979. Mindat lists 3 worldwide localities all at volcanoes.

This is a small capsule of 2-3mm pieces.


Montdorite

Formula
KFe2+1.5Mn2+0.5Mg0.5Si4O10(F,OH)2 
Crystal System
Monoclinic 
Crystal Habit
Microscopic Crystals 
Color
green, brownish green 
Class
Monoclinic - Prismatic 
Hardness
Collection
Phillips Collection
Special Info
Type Locality

Murmanite

#PD34724
Locality
Lovozero Massif, Kola Peninsula, Russia 
Formula
Na2Ti2(Si2O7)O2·2H2
Availability
Sold
Size
4 x 3 x 2.5 cm - Miniature 

Murmanite is NOT a mica but is a sorosilicate and is triclinic and contains Nb-Ti in large platy aggregates. Rare as crystals - lilac to pink ot purple in nepheline syenites and their pegmatites asccording to Bernard and Hyrsl. Looks micaceous but is not, although does posses a distinct basal cleavage.

 


Murmanite

Formula
Na2Ti2(Si2O7)O2·2H2
Crystal System
Triclinic 
Crystal Habit
Tabular, Massive 
Cleavage
Perfect, None, None 
Luster
Vitreous - Greasy 
Color
pink, bright pink, silvery, yellow, brown 
Streak
white 
Class
Triclinic - Pedial 
Fracture
Brittle - Uneven 
Hardness
2.5-3 
Collection
Phillips Collection

Muscovite

var. fuchsite - #PD34692
Locality
Binntal, Wallis, Switzerland 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
6 x 4 x 2 cm - Sm Cabinet 

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

Rich chromium 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
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On Dakota Matrix
Previously Sold Muscovite
On Dakota Matrix
Other Available Muscovite
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Mindat
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Muscovite

var. fuchsite with Corundum - #PD34722
Locality
Rutherford Co., North Carolina, United States 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
6.5 x 5 x 3 cm - Sm Cabinet 

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

Green flakes of chromium rich Muscovite with red corundum.


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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