This 6.46 carat cabochon from San Pedro Mountain is an extraordinary and ultra-rare optical specimen—an iridescent andradite garnet exhibiting a sharp, four-ray asterism across a luminous field of diffraction color. Measuring 10mm x 10.2mm x 6mm, the stone is expertly polished into a rounded dome that perfectly reveals the internal architecture responsible for its dual optical effects.

The dominant hues of this piece are bright emerald green and warm golden yellow, flashing with high saturation and metallic sheen. As the stone is rotated, vibrant secondary tones of cobalt blue and soft copper-orange emerge at the edges of the star, creating a shifting, spectral halo that moves with the light. The asterism itself—a four-ray cross of light—is produced by precisely aligned internal lamellar structures and fibrous domains that interact with directional illumination, projecting a radiant star across the surface. Unlike typical chatoyancy, which produces a single “cat’s eye,” this full asterism is geometrically rare and technically difficult to achieve, especially in andradite garnets.

Most asterized garnets from this source exhibit weak or scattered light effects, often with muted coloration. This stone, with its combination of clarity, bright diffraction, and a crisp, centered four-ray star, is a truly exceptional piece—one of only a handful known to exist with this level of performance.