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Uvarovite Garnet

Mineral

Ca3Cr2(SiO4)3

Also known as: Uvarovite

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Description

Uvarovite is a member of the garnet group, specifically the ugrandite series (uvarovite-grossular-andradite). It is distinguished by its brilliant emerald-green color, which is caused by the presence of chromium in its crystal structure. It typically forms as small, well-formed dodecahedral or trapezohedral crystals, often as drusy coatings on host rock. It is known for its high luster and excellent transparency when in crystal form. It is one of the rarer garnet species.

How to Identify

Color
Vibrant emerald-green to dark green. The color is diagnostic for uvarovite among garnets.
Luster
Vitreous (glassy) to adamantine (diamond-like) when well-crystallized.
Texture
Typically forms as small, distinct crystals, often as a druzy coating or embedded in a matrix. Individual crystals are usually euhedral.
Crystal Form
Cubic system, commonly forming dodecahedra or trapezohedra, or combinations thereof. Crystals are typically small, often less than a few millimeters.
Cleavage
None. Garnets are known for their lack of cleavage.
Geological Environment
Found in chromium-rich metamorphic rocks, particularly serpentinites, chromitites, and altered ultramafic rocks. Also occurs in skarns and hydrothermal veins associated with these environments.

Key Facts

  • Hardness: 6.5 - 7.5 on the Mohs scale
  • Specific Gravity: 3.41 - 3.85 (typically around 3.77)
  • Crystal System: Cubic
  • Color: Emerald-green to dark green
  • Luster: Vitreous to adamantine
  • Transparency: Transparent to translucent
  • Fracture: Conchoidal to uneven
  • Cleavage: None
  • Composition: Calcium chromium silicate

Quick Check

  • Color: Emerald-green
  • Luster: Vitreous to adamantine
  • Streak: White

Physical Characteristics

  • Crystal Habit: Typically dodecahedral or trapezohedral crystals, often forming drusy coatings or embedded grains. Crystals are usually small, rarely exceeding a few millimeters.
  • Cleavage Type: Absent (no cleavage)
  • Fracture Type: Conchoidal to uneven
  • Tenacity: Brittle
  • Luster Type: Vitreous to adamantine

Formation

Uvarovite is a calcium-chromium garnet that forms primarily in chromium-rich metamorphic rocks, such as serpentinites and chromitites, often associated with altered ultramafic rocks. It can also occur in skarns and hydrothermal veins where chromium is present. Its formation requires the presence of calcium, chromium, and silicon under specific pressure and temperature conditions typical of regional or contact metamorphism.

Usage

Uvarovite is primarily a collector's mineral due to its rarity and vibrant green color. Small, well-formed crystals are highly prized. It has limited industrial use due to its scarcity, though like other garnets, it possesses properties (hardness) that could theoretically make it suitable for abrasives, but its rarity precludes this. It is occasionally used in high-end jewelry, particularly as small druzy specimens or faceted stones, though faceted uvarovite is exceedingly rare.

Age Distribution

Uvarovite formation is not tied to a specific geological age but rather to specific geological processes involving chromium-rich environments, which can occur across various geological eras.

Where to Find

Saranovskoye Mine, Perm Krai, Ural Mountains, Russia

Historically the most significant locality, known for producing some of the finest uvarovite specimens, often as brilliant green druzy coatings on chromite.

Outokumpu, North Karelia, Finland

Another classic locality, producing good quality uvarovite crystals in association with chromite and other metamorphic minerals.

Jeffrey Mine, Asbestos (now Val-des-Sources), Quebec, Canada

Known for producing uvarovite in serpentinite, often associated with grossular garnet and chromite.

Bushveld Complex, Limpopo Province, South Africa

Occurrences in chromitite layers within this large igneous complex.

Turkey

Various localities, particularly in chromite deposits.

Norway

Occurrences in metamorphic rocks.

Finding Tips

Geological Context

Focus your search in areas known for chromium-rich metamorphic rocks, such as serpentinites, chromitites, and altered ultramafic complexes. Look for contact zones where these rocks have undergone metamorphism.

Associated Minerals

Uvarovite is often found in association with chromite, diopside, tremolite, serpentine minerals, and sometimes other garnets like grossular. Identifying these associated minerals can indicate a favorable environment.

Visual Identification

Look for small, sparkling emerald-green crystals, often forming a druzy crust on a darker matrix (typically chromite). The color is highly distinctive.

Microscope/Loupe

Due to the typically small size of uvarovite crystals, a hand lens (10x) or a microscope is often necessary to appreciate their form and color fully.

Safety Precautions

When collecting in serpentinite or altered ultramafic environments, be aware that asbestos minerals (e.g., chrysotile, tremolite, actinolite) can be present. Always wear appropriate personal protective equipment (PPE), including a respirator, eye protection, and gloves, and avoid disturbing friable material. Do not dry-brush specimens from such environments. Uvarovite itself is not hazardous, but its host rock may contain hazardous minerals.

Similar Rocks

Grossular Garnet

Ca3Al2(SiO4)3

Also known as: Grossular

Andradite Garnet

Ca3Fe2(SiO4)3

Also known as: Andradite

Diopside

CaMgSi2O6

Also known as: Chromian Diopside

Emerald

Be3Al2(SiO3)6

Also known as: Beryl (chromium-rich)

Scientific Classification

Mineral Class
Silicates
Group
Garnet Group (Ugrandite Series)
Crystal System
Cubic
Chemical Formula
Ca3Cr2(SiO4)3
Composition
Calcium aluminum silicate with chromium substituting for aluminum. End-member formula is Ca3Cr2(SiO4)3, but solid solution with grossular (Ca3Al2(SiO4)3) is common.

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