Sonoran Sunset Jasper

Sonoran Sunset Jasper, also marketed as Sonoran Sunset or Sonora Sunset, is a striking copper-ore rock from the Milpillas mine in Sonora, Mexico. Its dramatic red-and-green coloring comes from the minerals cuprite (red copper oxide) and chrysocolla (green copper silicate) intergrown in a silica-rich matrix.

Despite the 'jasper' trade name, it is a copper mineral assemblage rather than pure jasper, which gives it both its intense color and a somewhat softer, more variable hardness. The sunset effect, fiery red blending into green, makes it a sought-after lapidary material.

Sonoran Sunset formed in the oxidized zone of a copper deposit in Sonora, Mexico. As copper sulfide ores weathered near the surface, copper-bearing fluids reacted with oxygen and silica to crystallize secondary minerals.

Cuprite precipitated as deep red copper oxide, while chrysocolla formed as green to blue-green hydrated copper silicate; both were cemented within silica and host rock. This supergene enrichment process, common to many copper mines, produced the intertwined red and green zones that give the stone its sunset appearance.

Look for vivid red and green areas, often with black and earthy tan matrix, that together create a sunset-like contrast.

• Hardness: roughly 4-6 and variable, because cuprite and chrysocolla are softer than the silica matrix; harder than chrysocolla alone where well silicified.
• Streak: cuprite gives a brownish-red streak; chrysocolla a pale blue-green.
• Look-alikes: sonoran sunrise is essentially the same material; true jasper is harder and lacks the copper-red cuprite. The red cuprite component is diagnostic and may show submetallic to adamantine luster.

Sonoran Sunset is a popular but somewhat delicate lapidary stone used for cabochons, pendants, and collector specimens. Because of its softer copper-mineral content it is often stabilized to improve durability before cutting.

It is valued chiefly for its color rather than wearability and is best set in protective mountings or used in earrings and pendants. Metaphysically it is associated with vitality and emotional balance, traditional beliefs rather than scientific facts.