Tourmaline — Species Overview

(Complex Borosilicate · Variable Composition)

Tourmaline is one of the most chemically diverse gem species, resulting in an extraordinary range of colors. Popular colors include the electric blue of Paraiba, stately deep blue of indicolite, to the rich reddish purple of rubellite to a variety of soft pastels. It is rare to find clear tourmaline!

Tourmaline shows varying levels of pleochlorism, meaning viewing the crystal from one direction will show one color when viewed down the length of the crystal and will show when viewed from the side. Some tourmaline have what is called a "closed C" axis.  These crystals are black or near black when viewed down the length of the crystal.  This necessitates some specific cuts to prevent an overly dark stone. That said, tourmaline does come in solid black which can make for a striking piece!

Origins

Tourmaline forms in granitic pegmatites and metamorphic rocks. Notable sources include:

• Brazil
• Afghanistan
• Pakistan
• Mozambique
• Nigeria
• United States (California, Maine)

Each locality produces distinct color profiles.

Durability & Wearability

• Hardness: 7–7.5 on the Mohs scale
• Good toughness
• Strong pleochroism for lively color shifts
• Suitable for rings, pendants, earrings, and statement cuts

Tourmaline’s color diversity makes it one of the most expressive gem species.

Synthetics & Treatments

• Synthetic tourmaline is not commercially produced for the jewelry market.
• Common treatments include:
  • Heat to improve color
  • Irradiation for pinks (stable and accepted)
• All stones from Mossy Duck Gems are clearly labeled if treated.