Systematic Micaceous Minerals

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Annite

#PD34677

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Locality: Poudrette quarry, Mont Saint-Hilaire, Montérégie, Québec, Canada
Formula: KFe²⁺₃(Si₃Al)O₁₀(OH)₂
Availability: Sold
Size: 3.5 x 2.5 x 0.6 cm - Miniature

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Trioctahderal. For more information on Mica minerals and other phyllosilicates please reference our article - Click Here.

Annite is the iron rich, OH end member, of the Biotite- Phlogopite series. Common in schists, worldwide, up to 3m crystals in granites of Cape Ann near Rockport, Mass. USA, crystals up to 15cm from MSH (Bernard & Hrysl). Handbook of Mineralogy - pseudohexagonal outlines, and foliated masses, in Mg poor igneous and metamorphc rocks.

This specimen is only a small dark cleavage plate.

Annite

Formula: KFe²⁺₃(Si₃Al)O₁₀(OH)₂
Crystal System: Monoclinic
Cleavage: Perfect, None, None
Luster: Sub Metallic
Color: reddish brown, black
Streak: brownish white
Class: Monoclinic - Prismatic
Hardness: 2.5-3

Collection: Phillips Collection

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

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Anthophyllite

#PD34726

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Locality: Ilmen Mountains, Chelyabinsk, Southern Urals, Russia
Formula: □Mg₇Si₈O₂₂(OH)₂
Availability: Sold
Size: 4 x 3 x 2.5 cm - Miniature

Not a Mica, nor a phyllosilicate. Anthophyllite is a inosilicate - 2D infinite chains of silicate tetrahedra, which, morphologically resemble a phyllosilicate network. Anthophyllite occurs as bladed aggregates, much like this specimen, and on a smaller scale shows lamellar with elastic fibers and easy to mistake for a mica mineral.

Typically found in medium to high grade metamorphic amphibolites and gneisses. Associated with talc, chlorite, and micas. (Handbook of Mineralogy).

This specimen is a tight aggregate as that described above.

Anthophyllite

Formula: [box]Mg₇Si₈O₂₂(OH)₂
Crystal System: Orthorhombic
Crystal Habit: Fibrous, Lamellar, Massive
Cleavage: Perfect, Distinct, Distinct
Luster: Vitreous - Pearly
Color: white, greenish gray, green, clove brown, brownish green
Streak: gray
Class: Orthorhombic - Dipyramidal
Fracture: Conchoidal
Hardness: 5-6

Collection: Phillips Collection

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

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Astrophyllite

#PD34680

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Locality: Khibiny Massif, Kola Peninsula, Russia
Formula: K₂NaFe²⁺₇Ti₂(Si₄O₁₂)₂O₂(OH)₄F
Availability: Sold
Size: 4 x 2 x 0.6 cm - Miniature

Astrophyllite is NOT a mica but is an inosilicate, which can resemble mica plates in hand specimen, as is the case. Astrophyllite has a perfect cleavage, can be split like a mica in thin sheets, but is very brittle (Ency. of Minerals). The color is much like a mica also being a bronze to orange yellow. Usually found in pegmatites of nepheline syenites, alkaline granites of MSH and Magnet Cove (typical for titanium minerals). Finest crystals come from Khibiny massif (Bernard & Jaroslav).

This is a smaller specimen but with beautiful elongated bronze crystals to 1cm.

Astrophyllite

Formula: K₂NaFe²⁺₇Ti₂(Si₄O₁₂)₂O₂(OH)₄F
Crystal System: Triclinic
Crystal Habit: Bladed, Stellate, Crystalline - Fine
Cleavage: Perfect, None, None
Luster: Adamantine - Pearly
Color: brown, brownish red, bronze yellow, gold yellow
Streak: yellowish brown
Class: Triclinic - Pedial
Fracture: Brittle
Hardness: 3-3.5

Collection: Phillips Collection

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

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Biotite

series - #PD34672

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Locality: Franklin, Sussex Co., New Jersey, United States
Availability: Sold
Size: 6 x 4.5 x 4 cm - Sm Cabinet

Phyllosilicate - Monoclinic - Mica group member. Ordinary (True or Common) Mica - Trioctahderal. For more information on Mica minerals and other phyllosilicates please reference our article - Click Here.

Biotite has historically been treated as an individual mineral species and also treated as a generic dark mica in the field for those geologist without the aid of a portable XRD, which none of us had. Rieder et. al in the Canadian Mineralogist v. 36 (1998), reclassified and placed Biotite within the Annite-Phlogopite series..

This specimen is just a nice chunk with serious dark cleavage planes.