Brown and beige banding across a polished face, with the raw outer rind left intact.
These are iron colours. Agate takes its warm tones from iron oxides carried in by the water that filled the cavity, and the shade depends on how much arrived and what state the iron was in when it did. More oxidised gives redder browns, less gives the yellows and beiges. Each band is a separate delivery with its own chemistry, which is why the colour steps rather than blends.
It is also the honest palette. Grey, white, red and ochre are what untreated Brazilian agate actually looks like, and they are the tones collectors of natural material look for precisely because they cannot be faked convincingly. Dye produces an evenness that the real thing never quite has.
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: 10.35 x 7.2 x 12.8 cm
Weight: 625 g Note: Cut face polished, exterior left natural
You will receive the exact piece photographed.