This beautifully polished 3.7 carat cabochon from the famed San Pedro Mountains in Santa Fe County, New Mexico, is a rare example of iridescent andradite exhibiting a sharply defined four-ray asterism—a phenomenon exceptionally difficult to achieve in this garnet variety.

Measuring 9.75mm x 8.15mm x 4.15mm, the stone is cut with a balanced and intentional shape that perfectly reveals both the surface iridescence and the optical alignment responsible for the star effect. The asterism appears as a crisp, floating cross of light, dancing across the gem’s surface under a focused beam—an extremely elusive feature in andradite garnet, even from this world-class locality.

The San Pedro deposit is renowned for producing some of the finest examples of lamellar diffraction in garnet, with spectral rainbows in hues of violet, gold, green, and blue caused by nanoscale exsolution textures in the crystal. However, the presence of structured fiber-like domains oriented in just the right way to create a coherent, four-pointed star is almost unheard of. This makes "Star of San Pedro" not just a gem, but a true mineralogical anomaly—an intersection of geological luck and lapidary precision.

A masterpiece of natural optics and one of the very few known sharp four-ray andradite asterisms ever recorded from this locality