White through the whole polished face, with the raw rind left on.
White is information rather than an absence of it. Agate gets its colour from whatever the water was carrying alongside the silica, mostly iron for the reds and browns, manganese for the darker tones. A white geode means the water arrived carrying almost nothing else. Just silica, over and over, for as long as it took to fill the cavity.
That makes the banding easier to read than on a coloured piece, because there is nothing competing with it. You are looking at structure on its own. The rhythm of deposition, where it paused, where it sped up, and where the last of the silica gave up and finished as crystal instead of a smooth layer.
Mineral: Agate, banded chalcedony (silicon dioxide, SiO₂)
Crystal system: Trigonal
Origin: Rio Grande do Sul, Brazil
Hardness: 6.5 to 7 on the Mohs scale; durable, though the polished face will dull if knocked about
Treatment: None
Dimensions: 18.5 x 9.35 x 21 cm
Weight: 2.69 kg Note: Cut face polished, exterior left natural
You will receive the exact piece photographed.