Natural Tanzanite: 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 Tanzanite, discovered in Tanzania in the 1960s, is a variety of zoisite known for its striking blue and violet colors. With a hardness of 6 to 7 on the Mohs scale, it offers moderate durability, making it suitable for various jewelry applications. Tanzanite's unique trichroism allows it to exhibit different colors when viewed from different angles, adding to its allure. As one of the most sought-after gemstones, understanding its characteristics, sourcing, and market trends is crucial for anyone involved in its trade or collection.
Physical Properties and Specifications
Chemical Composition: Ca₂Al₃(SiO₄)(Si₂O₇)O(OH)
Hardness: 6 - 7 on the Mohs scale
Crystal System: Orthorhombic
Refractive Index: 1.69 - 1.70
Specific Gravity: 3.35 - 3.40
Pleochroism: Strong, displaying blue, violet, and burgundy hues
Fluorescence: Weak fluorescence under UV light
Cleavage/Fracture: Perfect cleavage in two directions, conchoidal fracture
Color and Quality Classifications
Available Color Ranges
Primary hues: Blue, violet
Secondary modifications: Purplish-blue, bluish-purple
Tone and saturation ranges: Light to dark tones with vivid saturation
Premium colors: Deep blue with strong violet undertones
Commercial grades: Light blue to medium blue shades
Clarity Characteristics
Typical inclusion types: Needle-like inclusions, silk
Clarity grading standards: Eye-clean to included
Source-specific features: Unique inclusions that may indicate the origin
Eye-clean criteria: No visible inclusions to the naked eye
Source Locations and Material
Historic sources
Tanzania (specifically the Merelani Hills)
Current production
The Merelani region remains the primary source of Tanzanite.
Source-specific characteristics
Tanzanite from different mining sites can exhibit variations in color and clarity.
Production trends
Increasing demand coupled with limited supply has led to rising prices, making Tanzanite more sought after.