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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.

Hendricksite

#PD34683
Locality
Franklin, Sussex Co., New Jersey, United States 
Formula
KZn3(Si3Al)O10(OH)2 
Availability
Sold
Size
9 x 8 x 6 cm - Sm Cabinet 
Special Info
Type Locality 

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Trioctahderal. Zinc occupies the (M) octahedral sites between the layers of (T) sites of Si and Al. K is the interlayer, making this an ordinary (True) mica. For more information on Mica minerals and other phyllosilicates please reference our article - Click Here.

Hendricksite is the only zinc bearing mica.

Occurs as plate-shaped or short prismatic crystals with rough terminations up to 40cm with a copper deep red to blackish red color. (Bernard & Hrysl). As pointed out by Reider et al (Can Min.), Hendricksite could be included in a solid solution series with "zincohendricksite" and "manganoanhendricksite" at the ends.

This is a large impressive specimen with large crystal sheets. Occurs in only a handful of worldwide localities.


Hendricksite

Formula
KZn3(Si3Al)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Euhedral Crystals, Aggregates, Foliated 
Cleavage
Perfect, None, None 
Color
copper brown, red, reddish black 
Streak
red brown 
Class
Monoclinic - Prismatic 
Hardness
2.5-3 
Collection
Phillips Collection
Special Info
Type Locality

Kinoshitalite

on Tephroite - #PD34810
Locality
Kamocho, Souraku Co., Kyoto Pref., Japan 
Formula
BaMg3(Si2Al2)O10(OH)2 
Availability
Sold
Size
4 x 3 x 3 cm - Miniature 

Phyllosilicate - Monoclinic - Mica group member. Brittle Mica - Trioctahderal. Barium occupies the Interlayer cation positions with Mg at the (M) sites.  May contain Mn and Ti. For more information on Mica minerals and other phyllosilicates please reference our article - Click Here.

Occurs as scales to 1mm, yellow-brown, in Mn-rich, Mn bearing marbles and skarns and in metamorphc granulite facies of Mn ore (Bernard & Hrysl). Also with haussmanite, tephroite ore in Japan. Only 2 US localities  and Langban per Mindat, no shitalite.

This specimen shows tiny yellowish platelets.


Kinoshitalite

Formula
BaMg3(Si2Al2)O10(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Scaly 
Cleavage
Perfect, None, None 
Luster
Vitreous (Glassy) 
Color
yellow brown, colorless 
Streak
yellow white 
Class
Monoclinic - Prismatic 
Fracture
Brittle 
Hardness
2.5-3 
Collection
Phillips Collection

Lamprophyllite

with Aegerine - #PD34670
Locality
Yukspor Mt, Khibiny Massif, Kola Peninsula, Russia 
Formula
Na3(SrNa)Ti3(Si2O7)2O2(OH)2 
Availability
Sold
Size
4.5 x 4.5 x 5 cm - Miniature 

Lamporphyllite is a sorosilicate containing Sr, Ba and Titanium and is NOT a mica nor micaceous. Bernard and Hyrsl describe Lamprophyllite as elongated crystals, golden to dark brown with a perfect {100} cleavage. It is an accessory mineral in nepheline syenites and their pegmatites.

This is a really handsome specimen with good crystals to 3cm resembling phlogopite in appearance only and is associated with Aegerine.


Lamprophyllite

Formula
Na3(SrNa)Ti3(Si2O7)2O2(OH)2 
Crystal System
Monoclinic 
Crystal Habit
Radial, Stellate, Acicular 
Cleavage
Good, None, None 
Luster
Vitreous - Pearly 
Color
yellow, brown 
Streak
brownish white 
Class
Monoclinic - Prismatic 
Fracture
Brittle 
Hardness
2.5 
Collection
Phillips Collection

Lepidolite

#PD34723
Locality
Harding mine, Taos Co., New Mexico, United States 
Formula
K(Li,Al)3(Si,Al)4O10(F,OH)2  
Availability
Sold
Size
6 x 5 x 3.5 cm - Sm Cabinet 

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Trioctahderal Lepidolite lies on or close to the Trilithionite - Polylithionite join and is a light mica with substantial lithium.  Contain fluorine in the (A) position. For more information on Mica minerals and other phyllosilicates please reference our article - Click Here.

Can be easily distinguished from rgular mica by the flame test for lithium.

Found in complex zoned pegmatites.  Potassium is often replaced by Na, Rb, and Cs.

NIce purplish pink, crystalline mass.


Lepidolite

Formula
K(Li,Al)3(Si,Al)4O10(F,OH)2 
Crystal System
Monoclinic 
Crystal Habit
Platy, Foliated, Massive 
Cleavage
Perfect, None, None 
Luster
Vitreous - Pearly 
Color
colorless, gray white, lilac, yellowish, white 
Streak
white 
Class
Monoclinic 
Fracture
Uneven 
Hardness
2.5-3 
Collection
Phillips Collection

Margarite

with Malachite - #PD34720
Locality
Chester Emery mines, Hampden Co., Massachusetts, United States 
Formula
CaAl2(Si2Al2)O10(OH)2 
Availability
Sold
Size
8 x 6 x 4.5 cm - Sm Cabinet 

Phyllosilicate - Monoclinic - Mica group member. Brittle - Dioctahedral. Al occupying the (M) octahedral positions with sub's of Lithium, Ca (or possibly Na) at the Interlayer spots, and hydroxyl at the (A) positions. Be and Al can replace Si at the (T) positions. For more information on Mica minerals and other phyllosilicates please reference our article - Click Here.

Rarely as good pseudohex. crystals, usually scaly or platy aggregates. Grayish pink to pink, but also yellowish. Occurs mainly with diaspore in contact metamorphic deposits (Bernard & Hrysl), also in chlorite schists (Mindat). Associated with corundum, diaspore, tourmaline, staurolite, glauphane, chlorite, and magnetite...in high aluminun deposits (Handbook of Min.).

This is a nice chunk with Malachite. Comes with a nice old Ward's label collected in 1939 which claims to contain Amesite. We did not see any of this!


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
Phillips Collection
Mineralpedia
View Margarite
On Dakota Matrix
Previously Sold Margarite
On Dakota Matrix
Other Available Margarite
WebMineral
View Margarite
Mindat
View Margarite

Margarite

#PD34799
Locality
Chester Emery mines, Hampden Co., Massachusetts, United States 
Formula
CaAl2(Si2Al2)O10(OH)2 
Availability
Sold
Size
11 x 7 x 5.5 cm - Cabinet 

Phyllosilicate - Monoclinic - Mica group member. Brittle - Dioctahedral. Al occupying the (M) octahedral positions with sub's of Lithium, Ca (or possibly Na) at the Interlayer spots, and hydroxyl at the (A) positions. Be and Al can replace Si at the (T) positions. For more information on Mica minerals and other phyllosilicates please reference our article - Click Here.

Rarely as good pseudohex. crystals, usually scaly or platy aggregates. Grayish pink to pink, but also yellowish. Occurs mainly with diaspore in contact metamorphic deposits (Bernard & Hrysl), also in chlorite schists (Mindat). Associated with corundum, diaspore, tourmaline, staurolite, glauphane, chlorite, and magnetite...in high aluminun deposits (Handbook of Min.).

This is a large foliated mass rich in Margarite.


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
Phillips Collection
Mineralpedia
View Margarite
On Dakota Matrix
Previously Sold Margarite
On Dakota Matrix
Other Available Margarite
WebMineral
View Margarite
Mindat
View Margarite

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