Natural Sapphire: Complete Guide for Trade, Jewelry, and Collections
This comprehensive guide provides everything you need to know about natural sapphire, for trade partners, jewelers, and collectors alike.
Overview
Natural sapphires are prized for their exceptional beauty and strength, making them a top choice for both jewelry and investment. These gemstones, typically blue but available in a range of colors, are formed deep within the Earth under high pressure and temperature. Their vibrant colors and remarkable clarity position them as a favorite among gem enthusiasts and jewelers alike.
Physical Properties and Specifications
Chemical Composition: Al2O3 (Aluminum Oxide)
Hardness: 9 on the Mohs scale
Crystal System: Trigonal
Refractive Index: 1.76 - 1.77
Specific Gravity: 3.95 - 4.03
Pleochroism: Weak to moderate (visible in some specimens)
Fluorescence: Generally inert, but some may fluoresce under UV light
Cleavage/Fracture: Indistinct cleavage; conchoidal fracture
Color and Quality Classifications
Available Color Ranges
Primary Hues: Blue, yellow, pink, green
Secondary Modifications: Violet, orange, gray
Tone and Saturation Ranges: Light to dark tones; vivid saturation is most desirable
Premium Colors: Deep blue, royal blue, and padparadscha (pink-orange)
Commercial Grades: Commercial-grade sapphires are typically lighter hues or have visible inclusions
Clarity Characteristics
Typical Inclusion Types: Rutile, silk, and crystal inclusions
Clarity Grading Standards: Graded from eye-visible to eye-clean
Source-Specific Features: Different sources produce varying inclusions
Eye-Clean Criteria: Must be free of inclusions visible to the naked eye
Source Locations and Material
Historic Sources: Kashmir, Burma (Myanmar)
Current Production: Sri Lanka, Madagascar, Thailand
Source-Specific Characteristics: Each location yields unique color and clarity traits
Production Trends: Increasing interest in ethically sourced sapphires