Design a high-detail 3D model of a luxury ring inspired by the Brazilian Cerrado biome. The ring features a vivid AAA+ pear-shaped emerald as the centerpiece, symbolizing nature's elegance and rarity. Crafted in polished 18k gold, the band is sleek and slightly organic, mimicking natural curves and textures found in Cerrado flora. Add subtle engraving details resembling native leaves or bark patterns. Lighting should highlight the gemstone's clarity and deep green hues. Photorealistic, suitable for rendering and jewelry prototyping.