Green Sapphire

Green sapphire is a green variety of corundum. Individual stones differ in tone, saturation, color distribution, and transparency, and may show secondary yellowish-green or bluish-green hues. These variations give every green sapphire its own appearance.

Mineralogically, green sapphire has the chemical formula Al₂O₃, the same as ruby and other sapphires. Its color may result from combined absorption involving iron, including yellow components associated with Fe³⁺ and blue components associated with Fe²⁺–Ti⁴⁺ pairs. Vanadium may also contribute in some stones. The mechanisms and proportions vary with the composition of each gem.

(Note: Information about meanings and beliefs reflects historical and cultural records and is not a scientifically proven property.)

Evaluating Green Sapphire Color

Some green sapphires have a relatively uniform color, while others show bands of color zoning or different shades when viewed along different crystallographic directions. A stone does not need to display visibly separate green, yellow, and blue regions to be classified as green sapphire.

The face-up appearance depends on the color and zoning within the rough, its crystal orientation, and the cutting proportions. These factors should be considered together when judging the visible color, brightness, and overall balance of an individual stone.

Shape, Cutting, and Design

Before cutting, a lapidary examines the rough shape, fractures, inclusions, color zoning, and crystal direction. The orientation is chosen to present an attractive green face-up color and useful brightness while limiting overly dark areas and retaining a practical amount of weight.

Green sapphire may be fashioned into oval, cushion, pear, round, cabochon, or other shapes. A cabochon has a smooth curved surface, while a mixed cut combines features from more than one faceting style.

Major Sources

• Thailand — Khao Ploi Waen, Chanthaburi: Green sapphire occurs alongside blue and yellow sapphire in corundum deposits associated with basalt.
• Australia: Green sapphires and sapphires displaying more than one color have been reported from Australian deposits.
• Northern Madagascar: Green sapphire has been reported from the Ambondromifehy area.
• United States — Montana: Light green sapphire has been reported from secondary deposits including Rock Creek, the Missouri River, and Dry Cottonwood Creek.

Internal Features and Inclusions

Green sapphire may contain mineral crystals, needles or silk, healed fractures or fingerprint inclusions, color zoning, and crystal-growth zoning. Gemologists assess these features together with optical properties and other test results when studying formation and distinguishing natural stones from synthetic or treated material.

Enhancement and Durability

Green sapphire may be unheated or heat-treated to modify color or clarity. Some material is treated by beryllium diffusion, in which heating is used with beryllium diffusion to alter color. Treatment status must be determined through appropriate gemological testing rather than appearance alone.

With a hardness of 9 on the Mohs scale, excellent toughness, and no cleavage, green sapphire is highly durable and suitable for jewelry worn regularly. As with any gemstone, exposed edges and heavily fractured stones should be protected by an appropriate setting.