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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.

Bityite

#RE7927
Locality
Harding mine, Taos Co., New Mexico, United States 
Formula
CaLiAl2(Si2BeAl)O10(OH)2 
Availability
Sold
Size
7.5 x 4.5 x 4.5 cm - Sm Cabinet 

Phyllosilicate - Monoclinic - Mica group member. Brittle Mica - Trioctahderal. For more information on Mica minerals and other phyllosilicates please reference our article - Click Here.

Bityite is a brittle mica since calcium cations assume the position in the interlayer instead of potassium. Beryllium replaces some of the silicon cations in the Tetrahedral positions and lithium takes on the positions in the Octahedral positions between the layers. One of a handful of lithium micas and the only one with essential beryllium.

Usually occurs as thin tabular and pseudohexagonal crystals to 2mm or as rosettes of dense or compact aggregates. Found sparingly in lithium rich pegmatites. (Encycl. of Min.). Weak yellow Fl.

This is a nice specimen with countless small 1-2mm white platy crystals on Biotite matrix. The Bityite exhibits weak yellow FL.


Bityite

Formula
CaLiAl2(Si2BeAl)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Encrustations, Platy, Pseudo Hexagonal 
Cleavage
Perfect, None, None 
Luster
Vitreous (Glassy) 
Color
brown white, colorless, yellow, pearl white 
Streak
white 
Class
Monoclinic - Prismatic 
Hardness
5.5 
Collection
Phillips Collection
Mineralpedia
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Mindat
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Celadonite

#PD34804
Locality
near Wadsworth, Washoe Co., Nevada, United States 
Formula
KMgFe3+Si4O10(OH)2 
Availability
Sold
Size
9 x 6 x 6 cm - Sm Cabinet 

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Dioctahderal. Mostly or ideally (?) aluminum free mica, with Mg & Fe in the (M) positions. For more information on Mica minerals and other phyllosilicates please reference our article - Click Here.

Per (Bernard and Hyrsl) usually as earthy fillings in amygdules and replacement after Augite. Very rare in minute crystals. Also as micaceous scales, widespread in formations of altered volcanic rocks on intermediate basaltic compositions and commonly associated with Montmorillonite.

This is a large chuck of basalt with the typical, dull green earthy celadonite filling amygdules.

Comes with old Hatfield Goudey specimen collected Sept. 9, 1949.


Celadonite

Formula
KMgFe3+Si4O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Earthy, Aggregates, Encrustations 
Cleavage
Perfect, None, None 
Luster
Earthy (Dull) 
Color
gray green, bluish green 
Streak
greenish white 
Class
Monoclinic - Prismatic 
Fracture
Earthy 
Hardness
Collection
Phillips Collection

Clintonite

var. seybertite - #PD34801
Locality
Amity, Orange Co., New York, United States 
Formula
CaAlMg2(SiAl3)O10(OH)2 
Availability
Sold
Size
9 x 9 x 5 cm - Sm Cabinet 
Special Info
Type Locality 

Phyllosilicate - Monoclinic - Mica group member. Brittle Mica - Trioctahderal. Ca, Na, K occupying the Interlayer positions while Mg, Fe2+, Al, Fe3+, Mn in the octahedral positions.

Occurs as tabular, pseudohexagonal, foliated, lamellar radiate crystals. Occurs cheifly in association with calcite, idocrase, grossular, spinel, phlogopite in crystalline limestones i.e. Crestmore (Encycl. of Min.)

This is a large older specimen from the type locality formerly called serberitite. 


Clintonite

Formula
CaAlMg2(SiAl3)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Massive - Lamellar, Radial 
Cleavage
Perfect, None, None 
Luster
Pearly 
Color
colorless, green, yellow, red, reddish brown 
Streak
colorless 
Class
Monoclinic - Prismatic 
Fracture
Brittle 
Hardness
4-5 
Collection
Phillips Collection
Special Info
Type Locality

Diaspore

manganoan - #PD34725
Locality
Glosam mine, Postmasburg, Northern Cape Province, South Africa 
Formula
AlO(OH) 
Availability
Sold
Size
5 x 4 x 3 cm - Miniature 

Diaspore is not a mica, but exhibits what some might think is a micaceous habit. Much like this specimen, Diaspore will have elongated plates, may be foliated, scaly with a perfect cleavage. It can occur with magnetite, corundum, spinel, chlorite, dolomite in metamorphic limestines or chlorite schists (Encycl. of Min.)


Diaspore

Formula
AlO(OH) 
Crystal System
Orthorhombic 
Crystal Habit
Platy, Tabular, Disseminated 
Cleavage
Perfect, Good, None 
Luster
Vitreous - Pearly 
Color
white, greenish gray, grayish brown, colorless, yellow 
Streak
white 
Class
Orthorhombic - Dipyramidal 
Fracture
Brittle - Conchoidal 
Hardness
6.5-7 
Collection
Phillips Collection
Mineralpedia
View Diaspore
On Dakota Matrix
Previously Sold Diaspore
On Dakota Matrix
Other Available Diaspore
WebMineral
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Mindat
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Eastonite

#PD34800
Locality
Williams quarry, Northampton Co., Pennsylvania, United States 
Formula
KAlMg2(Si2Al2)O10(OH)2 
Availability
Sold
Size
8 x 4 x 2.5 cm - Sm Cabinet 
Special Info
Type Locality 

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Trioctahderal. One half of the (T) sites occupied by Al. For more information on Mica minerals and other phyllosilicates please reference our article - Click Here.

Ideally all the Mg in the (M) sites and is actually in the Biotite series, yet is light in color. Previously thought to be a mixture of phlogopite and a new serpentine (AM Feb. '87 v. 72). Per Lauf (Coll. Guide to Mica Group Minerals) "considered by some author's to be aluminous variety of phlogopite.."

Only four localities worldwide (Mindat).


Eastonite

Formula
KAlMg2(Si2Al2)O10(OH)2 
Crystal System
Monoclinic 
Class
Monoclinic - Prismatic 
Hardness
Collection
Phillips Collection
Special Info
Type Locality
Mineralpedia
View Eastonite
On Dakota Matrix
Previously Sold Eastonite
On Dakota Matrix
Other Available Eastonite
WebMineral
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Mindat
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Glauconite

#34803
Locality
Wharf Mine, Lead, Lawrence Co., South Dakota, United States 
Availability
Sold
Size
10 x 4.5 x 5 cm - Cabinet 

Phyllosilicate - Monoclinic - Mica group member. Interlayer deficient - Dioctahedral. For more information on Mica minerals and other phyllosilicates please reference our article - Click Here.

Formerly considered a "hydromica". Occurs as pellets or globular grains and is the essential ingrediant of "greensands" which originated in shallow, warm seas of low sedimentation rate.

This specimen comes from the Wharf mine in the Black Hills as they were mining through lower Cambrian Deadwood Fm.


Glauconite

Formula
(K,Na)(Fe+++,Al,Mg)2(Si,Al)4O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Micaceous 
Cleavage
Perfect, None, None 
Luster
Earthy (Dull) 
Color
blue green, green, yellow green 
Streak
light green 
Class
Monoclinic - Prismatic 
Hardness

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