Natural Alexandrite: Complete Guide for Trade, Jewelry, and Collections
This comprehensive guide provides everything you need to know about natural rubies, 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.