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 structure. They are among the most common 'fancy color' diamonds, ranging from light yellow to intense, vivid canary yellow. Like all diamonds, they possess exceptional hardness, brilliance, and dispersion. Their value is determined by the intensity and purity of their yellow color, in addition to the traditional 4 Cs (carat, cut, clarity, color).

How to Identify

Color

Ranges from faint yellow to intense, vivid canary yellow. The color should be evenly distributed.

Luster

Adamantine (diamond-like), exceptionally brilliant.

Texture

Smooth to slightly rough on natural crystal faces; faceted surfaces are perfectly smooth.

Crystal Form

Typically octahedral, dodecahedral, or cubic crystals in their natural state. Often found as fragments or polished facets in jewelry.

Cleavage

Perfect octahedral cleavage in four directions {111}. This means it can be split along these planes, though it is extremely difficult due to its hardness.

Geological Environment

Primary deposits are found in kimberlite and lamproite pipes, which are ancient volcanic conduits. Secondary (alluvial) deposits are found in riverbeds and coastal plains where diamonds have been eroded from their primary sources and transported.

Key Facts

• Hardness: 10 (Mohs scale), the hardest known natural mineral
• Specific Gravity: 3.50-3.53 g/cm3
• Crystal System: Cubic (isometric)
• Color: Colorless, yellow, brown, green, blue, pink, red, black (yellow is due to nitrogen impurities)
• Luster: Adamantine
• Transparency: Transparent to opaque
• Fracture: Conchoidal to uneven
• Cleavage: Perfect octahedral {111}
• Composition: Pure carbon (C)

Quick Check

• Color: Yellow (faint to vivid)
• Luster: Adamantine (greasy on rough surfaces)
• Streak: Colorless (diamonds are harder than the streak plate)

Physical Characteristics

• Crystal Habit: Octahedral, dodecahedral, cubic, or combinations thereof; also massive, granular, or bort (poorly crystallized aggregates).
• Cleavage Type: Perfect in four directions, forming an octahedron.
• Fracture Type: Conchoidal to uneven, brittle.
• Tenacity: Brittle, despite extreme hardness.
• Luster Type: Adamantine (brilliant, like a polished diamond); unpolished crystals may appear greasy.

Formation

Yellow diamonds form deep within the Earth's mantle, typically at depths of 150-200 km, under extreme pressure (4.5-6 GPa) and high temperatures (900-1300 C). Their yellow color is primarily due to the presence of nitrogen impurities within the crystal lattice. These nitrogen atoms substitute for carbon atoms and absorb blue light, causing the diamond to appear yellow. The diamonds are then brought to the surface through explosive volcanic eruptions, primarily in kimberlite and lamproite pipes.

Usage

Yellow diamonds are highly prized as gemstones for jewelry due to their rarity, brilliance, and vibrant color. They are also used in industrial applications where their extreme hardness is beneficial, such as in cutting, drilling, and grinding tools, though industrial diamonds are typically lower quality and not necessarily yellow.

Age Distribution

Diamonds are typically billions of years old, with ages ranging from 990 million to 4.25 billion years. The host rocks (kimberlites, lamproites) are much younger, typically Mesozoic to Cenozoic.

Where to Find

Finding Tips

Similar Rocks

Scientific Classification

Mineral Class

Native Elements

Group

Carbon Group

Crystal System

Cubic (Isometric)

Chemical Formula

C

Composition

Pure carbon, with trace amounts of nitrogen (causing yellow color), boron (causing blue color), or other elements as impurities.

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