Natural Alexandrite: Complete Guide for Trade, Jewelry, and Collections

This comprehensive guide provides everything you need to know about natural alexandrites, for trade partners, jewelers, and collectors alike.

Overview

Natural alexandrite, a rare variety of chrysoberyl, is famous for its remarkable ability to change color, appearing green in daylight and shifting to red under incandescent light. This captivating phenomenon, combined with a hardness of 8.5 on the Mohs scale, makes alexandrite highly desirable. Originating in Russia, this gemstone has become a symbol of luxury and rarity, often associated with elegance and sophistication. Understanding its characteristics, sourcing, and valuation is crucial for anyone involved in the trade or collection of this exceptional stone.

Physical Properties and Specifications

  • Chemical Composition: Be₃Al₂(SiO₃)₆

  • Hardness: 8.5 on the Mohs scale

  • Crystal System: Orthorhombic

  • Refractive Index: 1.744 - 1.755

  • Specific Gravity: 3.68 - 3.73

  • Pleochroism: Strong, exhibiting green, yellow, and red hues

  • Fluorescence: Weak, typically showing a green glow under UV light

  • Cleavage/Fracture: Imperfect cleavage, conchoidal fracture

Color and Quality Classifications

Available Color Ranges

  • Primary hues: Green, red

  • Secondary modifications: Yellow, blue, brown

  • Tone and saturation ranges: Light to dark tones with vivid saturation

  • Premium colors: Strong green and red color transitions

  • Commercial grades: Light green to medium green and red shades

Clarity Characteristics

  • Typical inclusion types: Needle-like inclusions, silk, and liquid inclusions

  • Clarity grading standards: Eye-clean to included

  • Source-specific features: Unique inclusions that can indicate origin

  • Eye-clean criteria: No visible inclusions to the naked eye

Source Locations and Material

Historic sources

  • Russia (original source), Brazil, Sri Lanka, and Madagascar

Current production

  • Significant production is currently in Brazil and Sri Lanka.

Source-specific characteristics

  • Each location imparts distinct characteristics in color and clarity.

Production trends

  • Increasing interest in ethically sourced Alexandrite, with rising prices for high-quality stones.