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Micaceous Minerals

Saturday, 26 February 2022 08:00 AM

Introducing the "Micaceous Minerals" gallery which is part of our Special Edition galleries. This gallery contains mineral specimens for sale including lepidolite, margarite, murmanite, muscovite and more from places like Itinga, Minas Gerais, Brazil, Chester Emery mines, Hampden Co., Massachusetts, United States, Ilimaussaq complex, Narsaq, Kitaa prov., Greenland, Bahia, Brazil.

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Lepidolite

#43769

Details
Data
Provenance
Resources

Locality: Itinga, Minas Gerais, Brazil
Formula: K(Li,Al)₃(Si,Al)₄O₁₀(F,OH)₂
Availability: Sold
Size: 5 x 3.5 x 2 cm - Miniature

Purple "ball peen" habit Lepidolite.

"Lepidolite" was actually discredited as a unique mineral species. It is rather a "catch-all" name describing purple or lilac colored Muscovites belonging to the solid solution group of Polylithionite - Trilithionite, which are lithium rich micas. Lepidolite is often found in LCT (lithium - cesium - tantalum) pegmatites and can often be enriched in rubidium.

This particular habit of Lepidolite is often described as "ball-peen" Lepidolite for its similarity to the ball-peen hammer. David London describes this habit in his book "Pegmatites" and again sites differential or rapid growth in the constantly evolving chemical environment.

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

Mineralpedia: View Lepidolite
On Dakota Matrix: Previously Sold Lepidolite
On Dakota Matrix: Other Available Lepidolite
WebMineral: View Lepidolite
Mindat: View Lepidolite

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Lepidolite

#57610

Details
Data
Provenance
Resources

Locality: Itinga, Minas Gerais, Brazil
Formula: K(Li,Al)₃(Si,Al)₄O₁₀(F,OH)₂
Availability: Sold
Size: 12.5 x 12.5 x 0.5 cm - Cabinet

A large plate of purple Lepidolite to 12.5cm and 5mm thick. The first photo is backlit and shows the outline of the pseudohexagonal crystal form. In the last two photos the growth lines of the crystal can be seen.

Lepidolite falls within the series between Polylithionite and Trilithionite.

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

Mineralpedia: View Lepidolite
On Dakota Matrix: Previously Sold Lepidolite
On Dakota Matrix: Other Available Lepidolite
WebMineral: View Lepidolite
Mindat: View Lepidolite

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Margarite

#44217

Details
Data
Provenance
Resources

Locality: Chester Emery mines, Hampden Co., Massachusetts, United States
Formula: CaAl₂(Si₂Al₂)O₁₀(OH)₂
Availability: Sold
Size: 8 x 7 x 3 cm - Sm Cabinet

Large pale pink micaceous crystals to 1.5cm sandwiched between chloritic schists. Excellent specimen.

Margarite is a phyllosilicate - and a mica group member. It is defined as dioctahedral brittle mica. Aluminum occupies the (M) octahedral positions with possible subsitutes of lithium, calcium (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.

Large crystals of Margarite are rare. The mineral usually forms scaly or platy aggregates. Margarite typically occurs with diaspore in contact metamorphic deposits (Bernard & Hrysl), also in chlorite schists (Mindat). It is usually occurs associated with corundum, diaspore, tourmaline, staurolite, glauphane, chlorite, and magnetite...in high aluminum deposits (Handbook of Min.).

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: 4

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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Murmanite

#PD32101

Details
Data
Provenance
Resources

Locality: Ilimaussaq complex, Narsaq, Kitaa prov., Greenland
Formula: Na₂Ti₂(Si₂O₇)O₂·2H₂O
Availability: Sold
Size: 7 x 6 x 1.5 cm - Sm Cabinet

1mm pinkish plates of Murmanite scattered about matrix.

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 pinkish purple in nepheline syenites and pegmatites asccording to Bernard and Hyrsl. Murmanite looks micaceous but is not, although it does have a distinct basal cleavage.

Murmanite

Formula: Na₂Ti₂(Si₂O₇)O₂·2H₂O
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: Don Phillips Collection

On Dakota Matrix: Previously Sold Murmanite
On Dakota Matrix: Other Available Murmanite
WebMineral: View Murmanite
Mindat: View Murmanite

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Muscovite

var. fuchsite - #41238

Details
Data
Provenance
Resources

Locality: Bahia, Brazil
Formula: KAl₂(Si₃Al)O₁₀(OH)₂
Availability: Sold
Size: 6.5 x 4 x 3 cm - Sm Cabinet

Bright geen micaceous mass of fuchsite, a muscovite rich in chromium. It is rich green and exhibits flashy, wavy foliations.

Fuchsite contains up to 4.8% chromiun (Encycl. of Min.) imparting the green color and was originally described from Schwarzenstein in the Zillerthal and named after J. N. von Fuchs (Dana 6th Ed.).

Phyllosilicate - Monoclinic - Mica group member. It is classified as an ordinary (True or Common) Mica - Dioctahedral.