Oregon Sunstone

Oregon sunstone is a copper-bearing labradorite, a calcium-sodium plagioclase feldspar that crystallized inside basaltic lava flows in south-central and southeastern Oregon roughly one million years ago. As the parent magma rose through the crust, dissolved copper was held in the melt by high temperature and pressure. When the lava erupted and began cooling, plagioclase feldspar crystallized first as large phenocrysts while copper remained dissolved in the surrounding liquid.

As cooling continued and the copper became oversaturated, it precipitated as native copper platelets directly inside the already-formed feldspar crystals. This is the key mechanism that sets Oregon sunstone apart: the copper is not a surface coating or fracture filling but a structurally oriented inclusion locked inside the feldspar lattice along specific crystallographic planes. Later erosion of the weathered basalt released the durable feldspar crystals into surface soils, where they are now mined from both in-place basalt and surface eluvial deposits.

Color in Oregon sunstone is a direct function of copper concentration and platelet size. Champagne and pale yellow stones contain dispersed sub-microscopic copper that tints the feldspar without visible schiller. Increasing copper content shifts color through pink and peach to deep orange and the prized cherry red. The largest copper plates, oriented parallel to a crystallographic face, produce the reflective schiller that flashes metallic gold or red when the stone is tilted. This is the only gem feldspar in North America colored by copper, and one of only a handful worldwide.

Oregon sunstone is identified by the combination of feldspar optical and physical properties with copper-driven color and schiller. Hardness of 6, specific gravity between 2.62 and 2.65, and the triclinic cleavage of plagioclase place it firmly in the labradorite family. The refractive index runs 1.563 to 1.572, higher than alkali feldspars like orthoclase. Most decisive is the schiller: tilt a faceted stone or cabochon in direct light and watch for directional metallic flashes that come from reflection off oriented copper plates inside the stone.

Under magnification, genuine Oregon sunstone shows copper platelets as hexagonal or triangular metallic inclusions scattered irregularly through the stone, often with slight variation in size and orientation. In dichroic red-green material, rotating the stone reveals distinct green and red zones along different crystallographic directions, a pleochroic effect caused by the interaction of light with aligned copper clusters. The bodycolor should gradate naturally through the stone, with richer color typically concentrated in the areas with densest copper inclusion.