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Questions and Answers
What is the chemical formula for Biotite?
What is the chemical formula for Biotite?
- K(Li,Al)3(Si,Al)4O10(F,OH)2
- K(Mg,Fe2+)3(Al,Fe3+)[(Al,Si)3O10](OH,F)2 (correct)
- K(Mg,Fe2+3)(Al,Fe3+)Si3O10(OH,F)2 (correct)
- KAl3Si3O10(OH)2
What is the hardness range of Biotite?
What is the hardness range of Biotite?
2.5 - 3
What is the primary rock type associated with Lepidolite?
What is the primary rock type associated with Lepidolite?
Igneous
Muscovite can appear in a variety of colors and forms.
Muscovite can appear in a variety of colors and forms.
What is the specific gravity range of Lepidolite?
What is the specific gravity range of Lepidolite?
The luster of Muscovite is ______.
The luster of Muscovite is ______.
Match the following minerals to their chemical formulas:
Match the following minerals to their chemical formulas:
Flashcards
Biotite Composition
Biotite Composition
Basic fluoro potassium, magnesium, iron aluminum silicate mica
Lepidolite Color
Lepidolite Color
Pink to purple lithium aluminum fluoro-silicate mica
Muscovite Color
Muscovite Color
Mica with variable colors due to chromium or manganese content.
Biotite Colors
Biotite Colors
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Lepidolite Colors
Lepidolite Colors
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Muscovite Colors
Muscovite Colors
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Biotite Environment
Biotite Environment
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Study Notes
Biotite
- Chemical formula: K(Mg,Fe2+3)(Al,Fe3+)Si3O10(OH,F)2; includes members of the Mica group.
- Members: Phlogopite, Siderophyllite, Eastonite, Annite, Fluorannite, Tetraferriannite.
- Composition: Basic fluoro potassium, magnesium, iron aluminum silicate.
- Colors vary: Black, dark brown, dark green, reddish black; lighter colors in members like Phlogopite and Eastonite.
- Streak: White; Hardness: 2.5 - 3.
- Crystal system: Monoclinic; forms include thick flakes, micaceous masses, and tabular shapes.
- Transparency ranges from translucent to opaque; specific gravity: 2.8 - 3.4.
- Luster: Pearly; Cleavage: 1,1; Fracture: uneven; Tenacity: sectile, elastic.
- Environmental context: Common in metamorphic rocks (schist, gneiss) and igneous rocks (granites, rhyolites); primary mica in rare earth pegmatites.
Lepidolite
- Chemical formula: K(Li,Al)3(Si,Al)4O10(F,OH)2; a lithium aluminum fluoro-silicate.
- Color typically ranges from pink to purple, with occasional light gray and yellow shades.
- Streak: White; Hardness: 2.5 - 3.
- Crystal system: Monoclinic; forms often as small, scaly crystals in dense aggregates.
- Transparency: Transparent to translucent; Specific gravity: 2.8 - 2.9.
- Luster: Pearly; Cleavage: 1,1; Fracture: uneven; Tenacity: sectile, elastic.
- Found primarily in high-lithium granite pegmatites, distinguishing its environmental preference.
Muscovite
- Chemical formula: KAl3Si3O10(OH)2; may contain chromium or manganese.
- Variable composition: K(Al,Cr,Mn)3Si3O10(OH)2; occurs in diverse colors, including colorless, white, beige, yellow, brown, gray, green, pink, purple, red, and black.
- Streak: Colorless; Hardness: 2 - 2.5.
- Crystal system: Monoclinic; forms thick flakes, micaceous masses, and unique aggregates (e.g., bladed crystals, star-shaped formations).
- Transparency: Transparent to translucent; Specific gravity: 2.7 - 3.0.
- Luster: Pearly; Cleavage: 1,1; Fracture: uneven; Tenacity: sectile, elastic.
- Essential in various geological settings, notably in granite pegmatites, contact metamorphic rocks, schists, and hydrothermal veins; significant deposits mainly come from granite pegmatites.
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