Indicolite

Indicolite (also spelled indigolite) is the blue variety of tourmaline, usually the elbaite species. Its color ranges from light greenish blue and teal through to deep indigo and violet-blue. Pure blue tourmaline is among the rarer and more valued tourmaline colors.

The blue color is caused by iron in the crystal structure. Many indicolites lean toward greenish blue, and the rarer, more saturated pure blue stones command higher prices. The copper-bearing neon blue tourmalines are classed separately as Paraiba.

Indicolite typically forms long prismatic crystals and shows particularly strong dichroism, so the same stone can look quite different shades of blue depending on orientation, a key consideration when cutting.

Indicolite forms in granitic pegmatites, crystallizing from boron-rich fluids in open pockets where iron is incorporated to produce the blue color. It commonly occurs with other elbaite colors and lithium-bearing pegmatite minerals.

The specific shade depends on the iron content and the oxidation state during growth, with variations producing greener or purer blue tones.

Notable sources include Brazil (Minas Gerais), Afghanistan, Pakistan, Madagascar, Nigeria, Mozambique, Namibia, and the United States (Maine and California).

Look for blue to greenish-blue prismatic crystals with a rounded triangular cross-section and strong lengthwise striations. Hardness is 7-7.5 with vitreous luster, white streak, and no cleavage.

Indicolite shows very strong dichroism, often appearing dark blue down the crystal length and lighter or greener across it. This strong pleochroism helps separate it from blue topaz (basal cleavage, heavier) and aquamarine (hexagonal beryl, weaker dichroism).

Apatite can mimic the blue but is much softer at 5. Copper-bearing Paraiba tourmaline has a far more intense neon glow; ordinary indicolite is more subdued and lab testing confirms the absence of copper.

Indicolite is a sought-after jewelry gemstone, faceted into rings, pendants, and earrings, and valued because true blue tourmaline is relatively scarce. It is an October birthstone option alongside other tourmalines and opal.

It is also collected as crystals and in multicolor specimens. Value depends on the purity and saturation of the blue, with vivid pure-blue stones priced well above greenish ones, plus clarity and size. Some indicolite is heat-treated to improve the blue.

Metaphysically, indicolite is associated with communication, intuition, and the throat. These meanings are traditional rather than scientific.