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Ruby in Fuchsite is a striking metamorphic rock characterized by the presence of opaque, pink to deep red ruby (corundum) crystals embedded within a vibrant green fuchsite matrix. Fuchsite is a chromium-rich variety of muscovite mica, which imparts the distinctive green color. The rock often exhibits a schistose or gneissic texture due to the alignment of mica flakes. Minor accessory minerals such as kyanite, rutile, and various amphiboles may also be present. The contrast between the red ruby and green fuchsite makes it highly sought after for aesthetic purposes.
How to Identify
- Color
- Dominantly green (fuchsite) with distinct pink to deep red (ruby) inclusions. White or grey areas may indicate other minerals like quartz or feldspar.
- Luster
- Fuchsite exhibits a pearly to vitreous luster, while ruby is typically vitreous to adamantine. The overall rock can appear somewhat shimmery due to the mica.
- Texture
- Often schistose or foliated, reflecting the alignment of mica flakes. Ruby crystals are typically anhedral to subhedral, appearing as opaque masses or hexagonal prisms within the matrix.
- Crystal Form
- Ruby crystals are usually massive, granular, or anhedral to subhedral hexagonal prisms. Fuchsite forms platy, micaceous crystals.
- Cleavage
- Fuchsite (muscovite) has perfect basal cleavage (one direction), allowing it to split into thin sheets. Ruby (corundum) has no cleavage but exhibits parting.
- Geological Environment
- Found in regionally metamorphosed chromium-rich ultramafic rocks, often associated with greenstone belts or ancient cratons.
Key Facts
- Hardness: Ruby: 9 (Mohs); Fuchsite: 2.5-3 (Mohs). The overall rock will have variable hardness.
- Specific Gravity: Ruby: 3.95-4.10; Fuchsite: 2.77-2.88. The rock's specific gravity will be an average of its components.
- Crystal System: Ruby (Corundum): Trigonal; Fuchsite (Muscovite): Monoclinic
- Color: Green (fuchsite) and pink to deep red (ruby)
- Luster: Pearly to vitreous (fuchsite), vitreous to adamantine (ruby)
- Transparency: Ruby: Opaque to translucent (in this form); Fuchsite: Translucent to opaque
- Fracture: Ruby: Conchoidal to uneven; Fuchsite: Uneven
- Cleavage: Ruby: None (parting present); Fuchsite: Perfect basal cleavage (one direction)
- Composition: Ruby: Aluminum oxide (Al2O3) with chromium impurities; Fuchsite: Hydrous potassium aluminum silicate (K(Al,Cr)2(AlSi3O10)(OH)2) with chromium substituting for some aluminum.
Quick Check
- Color: Green with red inclusions
- Luster: Pearly to vitreous (fuchsite), vitreous to adamantine (ruby)
- Streak: White (fuchsite), white (ruby)
Physical Characteristics
- Crystal Habit: Ruby: Massive, granular, anhedral to subhedral hexagonal prisms; Fuchsite: Micaceous, platy, foliated aggregates.
- Cleavage Type: Fuchsite: Perfect basal cleavage {001}; Ruby: No true cleavage, but exhibits parting on {1011} and {0001}.
- Fracture Type: Ruby: Conchoidal to uneven; Fuchsite: Uneven.
- Tenacity: Ruby: Brittle; Fuchsite: Flexible, elastic.
- Luster Type: Fuchsite: Pearly to vitreous; Ruby: Vitreous to adamantine.
Formation
Ruby in Fuchsite forms during regional metamorphism of chromium-rich ultramafic rocks (such as serpentinites or chromitites) that have been metasomatized. The chromium from the original ultramafic rock is incorporated into muscovite to form fuchsite, and into aluminum-rich minerals to form ruby (corundum). The presence of chromium is crucial for both the green color of fuchsite and the red color of ruby. This process often occurs under amphibolite to granulite facies metamorphic conditions.
Usage
Primarily used as an ornamental stone, for carving, cabochons, spheres, and other decorative items. It is popular in lapidary arts and as a collector's mineral specimen. It is not typically used for industrial ruby extraction due to the disseminated nature of the ruby crystals and the presence of softer fuchsite.
Age Distribution
Typically associated with ancient metamorphic terrains, often Precambrian to Paleozoic in age, where ultramafic rocks have undergone regional metamorphism.
Where to Find
Tanzania
One of the primary sources, particularly in the Manyara Region, where it is often found in association with other metamorphic minerals.
India
Significant deposits are found in various states, including Karnataka and Andhra Pradesh, often in ancient metamorphic terrains.
Brazil
Known for occurrences in Minas Gerais and other regions with similar geological settings.
Russia
Found in certain Ural Mountains localities.
Pakistan
Reported occurrences in metamorphic belts.
Finding Tips
Look for Green and Red Contrast
The most distinctive feature is the vibrant green matrix with embedded red crystals. This color combination is a strong indicator.
Check for Mica Sheen
The fuchsite component will give the rock a characteristic pearly or metallic sheen, especially on freshly broken surfaces or polished areas.
Test Hardness
Ruby is very hard (9 on Mohs scale), while fuchsite is much softer (2.5-3). This difference can be felt when scratching or carving, though care should be taken not to damage specimens.
Examine Crystal Habit
Look for the characteristic hexagonal or anhedral forms of ruby crystals within the micaceous matrix.
Geological Context
Search in areas known for regional metamorphism of ultramafic rocks, particularly those with chromium mineralization.
Similar Rocks
Ruby in Zoisite
Corundum (Ruby) in Zoisite
Also known as: Anyolite
Ruby in Kyanite
Corundum (Ruby) in Kyanite
Also known as: Ruby Kyanite
Green Aventurine
Quartz with Fuchsite inclusions
Also known as: Aventurine Quartz
Scientific Classification
- Mineral Class
- Ruby: Oxide; Fuchsite: Silicate (Phyllosilicate, Mica Group)
- Group
- Ruby: Corundum Group; Fuchsite: Muscovite Subgroup
- Crystal System
- Ruby: Trigonal; Fuchsite: Monoclinic
- Chemical Formula
- Ruby: Al2O3 (with Cr3+ impurities); Fuchsite: K(Al,Cr)2(AlSi3O10)(OH)2
- Composition
- Ruby: Aluminum oxide with trace chromium; Fuchsite: Potassium aluminum silicate with significant chromium substitution.
Explore Ruby in Fuchsite
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