Yellow Diamond

Description

Yellow diamonds are a variety of natural diamond characterized by their distinct yellow hue. This color is caused by the presence of nitrogen impurities within the diamond's crystal lattice. They are among the most common colored diamonds, yet still significantly rarer than colorless diamonds. Their brilliance, fire, and scintillation are comparable to colorless diamonds, making them highly sought after in the gem market. The intensity of the yellow color can range from faint yellow to vivid fancy yellow, with the latter being the most valuable.

How to Identify

Color

Ranges from faint yellow to light yellow, fancy light yellow, fancy yellow, fancy intense yellow, fancy vivid yellow, and fancy deep yellow. The color is typically uniform.

Luster

Adamantine (diamond-like), exceptionally brilliant.

Texture

Smooth to the touch when polished; rough diamonds may have a greasy feel.

Crystal Form

Typically forms in isometric crystal habits, most commonly octahedra, dodecahedra, and cubes, or combinations thereof. Macles (twinned crystals) are also common.

Cleavage

Perfect octahedral cleavage in four directions, meaning it can be split along specific planes parallel to the faces of an octahedron.

Geological Environment

Found in kimberlite and lamproite pipes, which are volcanic conduits that brought diamonds from the Earth's mantle to the surface. Also found in secondary alluvial deposits, where diamonds have been eroded from their primary sources and transported by rivers.

Key Facts

• Hardness: 10 on the Mohs scale (hardest known natural mineral)
• Specific Gravity: 3.50 - 3.53 g/cm³
• Crystal System: Isometric (Cubic)
• Color: Faint yellow to vivid fancy yellow, caused by nitrogen impurities.
• Luster: Adamantine
• Transparency: Transparent to translucent
• Fracture: Conchoidal to uneven
• Cleavage: Perfect octahedral in four directions {111}
• Composition: Pure carbon (C), with trace amounts of nitrogen causing the yellow color.

Quick Check

• Color: Yellow (various intensities)
• Luster: Adamantine
• Streak: Colorless (as it is harder than the streak plate)

Physical Characteristics

• Crystal Habit: Octahedral, dodecahedral, cubic, or combinations; also macles (twinned crystals) and irregular shapes.
• Cleavage Type: Perfect octahedral {111}
• Fracture Type: Conchoidal to uneven
• Tenacity: Brittle (despite extreme hardness, it can be fractured along cleavage planes or by sharp impact)
• Luster Type: Adamantine

Formation

Diamonds form under extreme pressure and high temperature conditions deep within the Earth's mantle, typically at depths of 150 to 200 kilometers (90 to 120 miles). These conditions are found in the cratonic roots of continental plates. The carbon atoms are bonded in a strong, isometric crystal lattice. Yellow coloration in diamonds is primarily due to the presence of nitrogen impurities within the crystal structure. Type Ia diamonds contain nitrogen atoms clustered together, while Type Ib diamonds have isolated nitrogen atoms, which tend to produce a more intense yellow color. These diamonds are brought to the Earth's surface through explosive volcanic eruptions, forming kimberlite and lamproite pipes.

Usage

Yellow diamonds are highly valued as gemstones in jewelry due to their rarity, brilliance, and unique color. They are also used in industrial applications where their extreme hardness is beneficial, such as in cutting, grinding, and drilling tools, although industrial diamonds are typically lower quality and not colored.

Age Distribution

Diamonds range in age from approximately 990 million years to over 4.2 billion years, with most commercial diamonds being between 1 billion and 3.5 billion years old.

Where to Find

Finding Tips

Similar Rocks

Scientific Classification

Mineral Class

Native Elements

Group

Carbon Group

Crystal System

Isometric (Cubic)

Chemical Formula

C

Composition

Pure carbon, with nitrogen impurities responsible for yellow coloration.

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