Uvarovite Mineral Overview
- Mineral name: Uvarovite
- Mineral class: Silicate (nesosilicate, garnet group – ugrandite series)
- Chemical formula: Ca₃Cr₂(SiO₄)₃
- Crystal system: Cubic (isometric)
- Mohs hardness: 6.5–7.5
- Color range: Bright green, emerald green, dark green
- Luster: Vitreous
- Streak: White
- Cleavage: None
- Fracture: Conchoidal to uneven
- Specific gravity: Approximately 3.7–3.8
- Transparency: Transparent to translucent (rarely opaque in aggregates)
- Common locations: Russia, Finland, Turkey, South Africa, United States
- Uses: Collector mineral, rare gemstone (limited)
- Similar minerals: Tsavorite (grossular), emerald, chrome diopside
Physical and Optical Characteristics
Uvarovite is distinguished by its intense green color, which is caused by chromium. Unlike many other garnets, it almost always occurs as small, well-formed crystals rather than large, massive aggregates.
Crystals are typically dodecahedral, forming sparkling drusy coatings on host rock. Individual crystals are usually small—often only a few millimeters across—but can be densely packed, creating a bright, glittering surface.
The luster is vitreous, and high-quality crystals can display strong brilliance. With a hardness of 6.5 to 7.5, uvarovite is relatively durable and resistant to scratching.
Like all garnets, it has no cleavage and breaks with a conchoidal to uneven fracture, contributing to its toughness.
Chemical Composition and Structure
Uvarovite is a calcium chromium silicate and is the chromium-rich endmember of the ugrandite garnet series.
Its structure consists of:
- Calcium (Ca) in the main cation sites
- Chromium (Cr³⁺) in the octahedral sites
- Isolated silicate tetrahedra (SiO₄)
Because chromium strongly influences color, even small variations can affect the intensity of the green hue.
Uvarovite forms limited solid solution with:
- Grossular (Ca₃Al₂(SiO₄)₃)
- Andradite (Ca₃Fe₂(SiO₄)₃)
However, pure uvarovite compositions are relatively common compared to other garnet endmembers.
Formation and Geological Occurrence
Uvarovite forms in chromium-rich environments, typically associated with ultramafic rocks.
Common formation settings include:
- Serpentinites and peridotites
- Metamorphosed ultramafic rocks
- Chromite-bearing deposits
It often develops as a secondary mineral in fractures and cavities within these rocks.
Associated minerals commonly include:
- Chromite
- Serpentine
- Magnetite
- Diopside
These associations reflect environments rich in chromium and magnesium.
Common Locations
Uvarovite is found in several notable localities:
- Russia: Ural Mountains (type locality and classic source)
- Finland: Known for well-formed crystals
- Turkey: Produces attractive specimens
- South Africa: Occurrences in chromium-rich deposits
- United States: Limited occurrences in ultramafic terrains
Russian specimens are especially well known for their bright green drusy coatings.
Uses and Practical Significance
Uvarovite has limited practical use but is valued for:
- Collector specimens: Highly sought after for color and crystal form
- Gemstone use (rare): Occasionally used in jewelry as drusy surfaces or small stones
Because crystals are typically small, it is rarely cut into traditional faceted gemstones.
Similar and Related Minerals
Uvarovite may be confused with other green minerals:
- Tsavorite (grossular garnet): Also green, but typically forms larger crystals and is more often faceted
- Emerald (beryl): Similar color but softer and with different crystal structure
- Chrome diopside: Green and found in similar environments, but has cleavage and different crystal habit
- Demantoid (andradite garnet): Green but often more yellowish and with different inclusions
Crystal habit (small dodecahedra) and association with ultramafic rocks are key distinguishing features.
Identification Notes for Collectors
- Look for bright green, small dodecahedral crystals forming drusy coatings
- Note association with chromite and serpentinite
- Check hardness (6.5–7.5) and absence of cleavage
- Observe strong, consistent green color due to chromium
- Consider locality, especially Ural Mountain specimens
Uvarovite is a distinctive garnet, recognized for its vivid chromium-green color and its tendency to form sparkling crystal coatings rather than large individual gems.