Agate-Banded Geode Half — Blue Chalcedony Ring, Amethyst Center, 16 lbs

Most geodes open to reveal one thing. This one reveals three. The outermost layer is dark volcanic matrix — charcoal basalt with patches of green mineral weathering across its surface, unworked and intact. Inside that, a continuous ring of translucent blue-grey chalcedony agate follows the full perimeter of the interior, smooth and watery in tone against the rough matrix behind it. That band gives way to a dense white quartz field that grows inward from every direction, and at the center, where the growth finally ran out of room, a pale lavender amethyst cluster took over — open-faced, glassy, and distinctly its own event. Three mineralogical zones, each formed at a different moment in the same slow process, all visible at once in a single cross-section.

The amethyst center on this specimen is larger and more developed than is typical for geodes at this scale — it occupies a genuine cavity rather than a surface deposit, with individual terminated points visible rather than just druzy coating. The blue chalcedony band is the piece's signature: that color, at that saturation, is a function of silica composition and trace mineral content that cannot be replicated or predicted. It is either there or it isn't. Here, it runs unbroken around the entire interior edge.

CONDITION

Good. Crystal field and chalcedony band intact throughout with no damage. The amethyst center cluster shows minor natural abrasion consistent with the open-cavity environment; the basalt matrix retains full natural texture.

DIMENSIONS / SPECIFICATIONS

• Height: 10½"
• Width: 9½"
• Depth (thickness): 2⅜"
• Weight: 16 lbs 1.7 oz
• Campbell's Soup Can (4" H) Shown for Scale