Girasol Opal

Girasol opal is a transparent to semi-translucent opal that shows a soft, floating bluish-white sheen or glow which appears to move as the stone or light is turned. The name comes from the Italian girasole, "turning toward the sun," referring to this drifting light effect.

Unlike precious opal, girasol's appeal is this milky adularescent-like glow rather than spectral play-of-color, though it is sometimes mildly opalescent. It is frequently confused with, and the term is sometimes applied to, girasol quartz and certain fire opals.

Much girasol opal on the market comes from Madagascar and Mexico.

Girasol opal forms by the low-temperature deposition of hydrated silica from groundwater in volcanic and sedimentary host rocks. Its characteristic bluish sheen results from the scattering of light (Tyndall/Rayleigh-type scattering) by extremely fine silica spheres and submicroscopic structure within the otherwise transparent body.

Where the silica is highly uniform and nearly inclusion-free, the stone is transparent with a faint internal glow rather than diffused opacity. Madagascar and Mexico are common sources of opal sold as girasol.

Note that some "girasol" on the market is actually a milky variety of quartz, which forms differently in pegmatitic and hydrothermal settings.

Look for a transparent to milky stone with a soft bluish-white glow that shifts with the light, a vitreous luster, white streak, and Mohs hardness near 5.5-6.5 (for true opal).

Important distinction: Girasol quartz is harder (7) and crystalline; girasol opal is softer and amorphous and may craze. Test hardness to tell them apart. Moonstone (feldspar) shows a similar floating sheen (adularescence) but is a feldspar with cleavage and hardness around 6-6.5.

The bluish floating glow without true spectral play-of-color, combined with opal-range hardness and possible crazing, indicates girasol opal.

Girasol opal is cut into cabochons and beads, and transparent material is faceted, for jewelry that highlights its ethereal floating glow. It offers a subtle, moonlit alternative to flashy play-of-color opal.

As an opal, it should be protected from impact, heat, and dehydration to prevent crazing. Buyers should clarify whether a "girasol" is opal or quartz, since durability and care differ.

Metaphysically it is associated with intuition and gentle energy (not a scientific claim). It is popular in artisan and bohemian jewelry.