Natural Tourmaline: 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 Tourmaline is a diverse gemstone group known for its remarkable color variations, ranging from deep greens and blues to vivid pinks and yellows. With a hardness of 7 to 7.5 on the Mohs scale, Tourmaline is durable and suitable for a variety of jewelry applications. Its unique pleochroism allows it to exhibit different colors when viewed from different angles, adding to its allure. As a popular choice among jewelers and collectors alike, understanding Tourmaline's characteristics, sources, and market dynamics is crucial for anyone involved in its trade or collection.
Physical Properties and Specifications
Chemical Composition: Varied; common formulas include Na(Li,Al)₄(Al,Fe,Mn)₃Si₆O₁₈(BO₃)₃(OH)₄
Hardness: 7 - 7.5 on the Mohs scale
Crystal System: Hexagonal
Refractive Index: 1.620 - 1.700
Specific Gravity: 2.83 - 3.20
Pleochroism: Strong, exhibiting different colors depending on the angle of view
Fluorescence: Generally inert, but some specimens may show weak fluorescence
Cleavage/Fracture: Indistinct cleavage, conchoidal fracture
Color and Quality Classifications
Available Color Ranges
Primary hues: Pink, green, blue, yellow, red, and black
Secondary modifications: Brown, gray, and multicolored (bicolor and tricolor)
Tone and saturation ranges: Light to dark tones with vivid saturation
Premium colors: Deep pink, rich green, and intense blue
Commercial grades: Light shades and less saturated colors
Clarity Characteristics
Typical inclusion types: Needle-like inclusions, color zones, and internal fractures
Clarity grading standards: Eye-clean to included
Source-specific features: Unique inclusions that may indicate origin
Eye-clean criteria: No visible inclusions to the naked eye
Source Locations and Material
Historic sources
Brazil, Afghanistan, Sri Lanka, and Madagascar
Current production
Significant production is currently from Brazil, Nigeria, and Mozambique.
Source-specific characteristics
Each location imparts distinct characteristics in color and clarity.
Production trends
Increasing demand for Tourmaline has led to rising prices, especially for high-quality specimens.