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Micaceous Minerals 3

Sunday, 19 February 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.

Margarite

#DP46710
Locality
Chester Emery mines, Hampden Co., Massachusetts, United States 
Formula
CaAl2(Si2Al2)O10(OH)2 
Availability
Sold
Size
5 x 3 x 3 cm - Miniature 

Light purplish micaceous crystals to 2cm. This is the same as the prior Margarite in this Special Edition, just a bit smaller.


Margarite

Formula
CaAl2(Si2Al2)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Lamellar, Massive - Lamellar, Scaly 
Cleavage
Good, None, None 
Luster
Pearly 
Color
white, gray, pinkish gray, yellowish gray 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Brittle 
Hardness
Collection
Polak Collection
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Masutomilite - 46464
Masutomilite - 46464

Masutomilite

#46464
Locality
Mokrusha pegmatite, Alabashka peg. field, Murzinka dist., Middle Urals, Russia 
Formula
KLiAlMn2+(Si3Al)O10(F,OH)2 
Availability
Sold
Size
6 x 4 x 2 cm - Sm Cabinet 
Special Info
XRD Confirmed 
Special Info
EDS Confirmed 

A purplish cleavable mass. The specimen was positively identified by Dr. Igor Pekov.

Masutomilite is a mica group member and an 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 
Special Info
XRD Confirmed
Special Info
EDS Confirmed

Montmorillonite

with Quartz - #PD34929
Locality
Newry Mica mine, Oxford Co., Maine, United States 
Formula
(Na,Ca)0.3(Al,Mg)2Si4O10(OH)2·nH2
Availability
Sold
Size
8 x 6 x 3.5 cm - Sm Cabinet 

Light pinkish clay mineral. Montmorillonite is a phyllosilicate and member of the smectite group. It is not a mica, and usually not confused as a mica, and is almost always in very fine aggregates. On a microscopic level you may see the basal cleavage confusing it with a mica.


Montmorillonite

Formula
(Na,Ca)0.3(Al,Mg)2Si4O10(OH)2·nH2
Crystal System
Monoclinic 
Crystal Habit
Earthy 
Cleavage
Perfect, None, None 
Luster
Earthy (Dull) 
Color
white, gray white, yellow, brownish yellow, greenish yellow 
Streak
white 
Class
Monoclinic - Prismatic 
Fracture
Earthy 
Hardness
1.5-2 
Collection
Phillips Collection
SOLD
Muscovite - 35305
Muscovite - 35305

Muscovite

var. fuchsite - #35305
Locality
Bahia, Brazil 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
9.5 x 6 x 2.5 cm - Cabinet 

Emerald green, coarse granular Muscovite with a chromium impurity imparting the rich green 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 
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Muscovite

#35313
Locality
Rodinha mine, Jenipapo dist., Itinga, Minas Gerais, Brazil 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
5 x 3.5 x 3.5 cm - Miniature 

Muscovite mica twinned in stellate habit. The "stars" are 1.5cm across.


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 
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On Dakota Matrix
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Muscovite

#37782
Locality
Aldeia do Eme mine, Conselheiro Pena, Minas Gerais, Brazil 
Formula
KAl2(Si3Al)O10(OH)2 
Availability
Sold
Size
8 x 4.5 x 4.5 cm - Sm Cabinet 

An excllent cluster of pseudohexagonal crystals to 4.5cm across. 


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

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